Your assumption is correct. The alicorn transformation can only be granted to ponies.

I'm not sure what you mean by the danger, in point 2. I can't think of a danger that fits all the criteria you mentioned. Military threat wouldn't affect other ponies, and envy would affect other races regardless of alicorn rule or not.

Point 4 is good, though it has a fairly easy answer: Ponies would have to be approved by someone (or multiple someones) trustworthy in order to be upraised, not merely by any alicorn. So, you would need to trust the pony to adhere to the laws, but you wouldn't need to trust them to have excellent judgement of their friends and their friends' friends and so forth. I think it's pretty obvious that there are far more of the former than the latter.

That's an excellent backup plan. Fortunately, with all the other replies in this thread, I'm unlikely to need a backup plan. That said, for the purposes of strengthening both sides, I'm likely to look for arguments to strengthen alicornism at some stage, and if that makes alicornism too powerful, I shall consider your idea as a way to bring parity back to the sides.

"If you are Christian, then you probably know the Bible in detail, you are probably familiar with a range of theological and apologetic texts"

I'll admit I don't have any statistics here, but from what I've seen heard, both first-hand and second-hand, Christians tend to be quite poor on average at knowing the Bible. I've never heard any evidence suggesting the average Christian has a detailed knowledge of the contents of the Bible, even if the kind of Christians who like to argue Christianity are more informed than most. (Similarly, argumentative atheists tend to have a better knowledge of the atheistic arguments than the average atheist.)

It's not even really about magical power. Within the world, it's about political power, and the fact that the alicorns are royalty. In reality, it's about the nature of the fanfiction. Much of the fanfiction is about the discussion and debate between the four princesses of Equestria. Therefore, any pony that isn't an alicorn tends to fade into the background a bit, taking the role of a driving force on the main characters. The main power that the alicorns have is the literary device of being major characters.

I spent two minutes arguing about why Discord was a stupid example, but then realised Discord is actually good now. Discord doesn't really stylistically fit into any of those five arguments, however. Looking at him, I imagine he would abstain from the issue. I simply don't see why he would care, period. The only thing he might do would be to try and get Fluttershy immortality, but even if he did take on that side, I don't see him entering the political arena. Adding an OC immortal isn't really something I want to do. For one, I suck at making characters, and for another, the thing I enjoy most about fanfiction is exploring the world that already exists.

The political opponents are really more of an obstacle than a character. In my opinion, they would be far better off as an abstraction: Instead of the Griffon Prince coming to Equestria to argue with the princesses, the argument is "The griffons won't be happy if we do this, and there could be consequences."

As for Twilight and Cadence, just because Twilight's bookish doesn't mean she doesn't care. I assume she'd be on the forefront of research to solve mass-transformation-related problems, but to do that, it's only logical that she convince the other princesses they should actually go ahead and agree to the transforming first. I agree that Cadence actually would be a likely candidate to take on the mantle of "We should transform everypony as fast as possible" but that argument is likely to be pretty soundly defeated in the first few chapters anyway. Thus, it's better for the fic if Cadence has a pro-alicorn, but reasonably well thought out view. It's okay for Twilight to hold that view for a while and still be rational, because it's a snap judgement: She only finds out that Cadence and herself are immortal when she actually gets transformed. Before Celestia mentions it, Twilight assumes that only Celestia and Luna are immortal.

Essentially, it would make sense for Cadence to be an irrational character, but I think the fic is overall better to give Cadence a slightly different character and allow her to be more rational, and thus increase the amount of solid discourse within the story. It's a sacrifice, but I think it's one worth making. I actually think the irrational view is more in Cadence's character, but the alicorns are already being bumped up in rationality to begin with: One more won't be too odd. And a rationalist!Cadence would likely take on the role of "Do it once we're sure it will work." I actually have a scene I drafted out which has this particular argument in it, which I'll send to you as an example of Cadence's character. (I don't want to make my comments TOO long in length, we already have a massive comment chain as it is!)

That...is actually pretty brilliant. I was originally going to have Celestia be opposed to the idea of alicornification, but I may have Celestia change her mind to this. Cadence has the view of "We should make absolutely sure we've concluded things will work before proceeding", which is likely to take decades, but not millenia. Twilight starts out with the view of "We should start right now, why the hell are we even hesitating?"

This is partly because of the big red flag of having the protagonist share my personal beliefs. In this fanfic, it's unavoidable, however. Twilight is meant to be fairly rational, and thus, is meant to believe what's correct, at least eventually. Obviously, I think that what I believe is correct, or I wouldn't believe it. Starting Twilight out with a more reckless view, where my own view is closer to the Cadence stance, goes some way towards deflecting that problem.

Man, it's times like this I wish I had a fifth alicorn to throw in, because I have too many views I currently want to showcase front and centre.

"Do it, and do it now."

"Calculate everything out carefully, then act relatively decisively."

"Steadily make it happen, over several millenia, gradually making it so that the very worst scum of society are still as harmonic as the best examples of pony virtue today."

"Don't do it, as we can't accurately calculate the risk."

"Don't do it. Don't even think about it. You saw what happened with Nightmare Moon, didn't you?"

Maybe I need a fifth main character, but I find the views are much more legitimised by having them be spoken by an alicorn, rather than a societal representative, who'll be representing various arguments like overpopulation, pushing forward magical research, attacking the culture of the various pony races, etc. And there are only four alicorns, and randomly adding a fifth is a move I simply refuse to make.

With the exception of the third view, i.e, the one you just gave me, I was originally going to have Twilight, Cadence, Celestia and Luna hold those four views, from most supportive to least supportive. But your argument is just too good not to be featured in the fanfiction.

The easiest solution is likely to be to merge Argument 4 and 5 together, leaving Luna as the only true anti-alicornifying one, with the remaining three each believing it should be done in different ways, but I worry that might turn the fanfic too much towards the pro-alicorn view. That said, I might be able to make up for this by having a disproportionate amount of the social representatives be opposed to the idea.

Fortunately, I now have enough arguments against alicornification to turn the fanfic into a good fight while still having the world the way I originally envisioned it. I doubt many people are going to say I'm making it too easy, what with all the arguments about social pressure, overpopulation, and potential for magical abuse. Plus, I'm adding something that we don't see often enough: At the beginning of the fic, the protagonist is simply WRONG. Twilight's belief is "We should charge ahead and turn everypony into alicorns as quickly as possible" and to me, that's actually very stupid. My own belief is that the best way forward involves care and caution, making sure things will work on a societal level before taking significant steps forward, and that's the belief Twilight will eventually take on.

(I know that it's a big warning sign to have my protagonist have the same beliefs as me, but I can't avoid it, since I want Twilight to be rational enough to eventually reach the right conclusion, and I obviously think my belief is correct, or else I'd believe something else. So, hopefully this helps with that problem.)

But thanks very much for your initial point, it definitely made me think much harder about the world, and how I wanted it to work. I likely would have taken your advice on if I hadn't received so many good arguments. In fact, I was originally going to give other ponies Celestia-like powers to counter this author bias until I was soundly defeated in a debate about alicornification with that prior, which therefore made me decide "Okay, it's not being too easy on myself to make alicorn magic a force multiplier, it's being too hard on myself to make every alicorn Celestia!"

Definitely possible. After all, I'm not going to ignore technical constraints. I just don't intend to invent them. Hell, I don't have to. The problem is hard enough as it is. (For example, overpopulation is a very difficult technical constraint, and it arises naturally from the logic inherent to the canon setting.)

I don't intend to write it in the fashion described (I.e, a largely linear story where Twilight and friends solve various technical constraints of alicornification in turn, being rewarded with immortality each time, until there aren't any left) but technical constraints such as social pressure, overpopulation, and potential for magical abuse will definitely appear within the fanfic: Logical constraints that are inevitably going to come up within the Equestria setting that are significant obstacles to Twilight's plan, but are not unbreakable. I'm even willing to accept the deathists winning if the plot turns on me and decides the protagonists shouldn't win, but I'm not going to render one side completely unable to fight back, which would happen if the ideal of mass alicornification is scientifically impossible.

Your idea for the more linear fic is quite a good one, and in the event that I was unable to get enough material for the deathists, I could have definitely gone with it. But between the arguments I've gotten so far, I have plenty of material to ensure a real battle between the ideologies, rather than "Twilight wins because deathism is stupid." If HPMOR has taught me anything about writing, it's that both sides have to have a strong argument for the story to be as good as it can be.

I actually don't know if I'll be able to have any sufficiently intelligent characters in the fanfiction who think that death is a bad idea at a base level though, rather than being simply too dangerous, difficult, or logistically impossible to eliminate. The closest is probably going to be Luna, who's going to have a very inflexible "It's too dangerous" view, due to her own experiences at turning into Nightmare Moon and almost destroying Equestria. The view of "Death is good and part of the natural order" will be expressed, but I don't think it fits any of the alicorns to have that viewpoint. A good example of a pony who could hold that view would be Applejack, but Applejack isn't exactly the kind of pony to be able to engage Twilight in logical debate and put up a good fight with logic alone.

For the purpose of this fanfiction, Celestia is able to uplift alicorns at a significantly higher rate than she currently is and other alicorns can either cast it, or learn to cast it. So logistically, it's possible to increase alicornification at an exponential rate. Call it somewhere between 6 and 12 casts a year, for now: The exact rate isn't all that important, what's important is that it can be done, which means arguments then shift to "Should it be done?"

As for the power vs. safety thing, I agree, that's definitely true, but what I was asking was, given this particular point on the spectrum, what would you think then? It's clearly too unsafe to make everyone gods, as you've demonstrated, and it's clearly perfectly safe if there's zero dangers to making alicorns at all. But if ponies are significantly more powerful as alicorns, and thus had the potential to do more damage both deliberately and accidentally, but most ponies didn't have the capacity to cause REALLY bad stuff to go down: What would your opinion be then?

I'll have to check out that comic if the Chrysalis argument comes up, I suppose.

I'm not sure what you mean by trying to exploit closed-loop time travel through travelling to the future. Do you mean using future sight to see a desirable future and then trying to get there?

As for time travel, in this particular fic, my best answer is simply "Hell no." If it comes up, Twilight and the alicorns can simply decide it's a Really Bad Idea to use it, and they're right, since nobody actually understands how the hell it works, because it violates causality in that fashion. Alternatively, I borrow an answer I saw in a fanfiction once: It can only be used once in a pony's lifetime. And, obviously, the alicorns being immortal and all wouldn't use up one of their precious uses of the spell for anything short of "The situation is hopeless, and Equestria is now 100% doomed." (That is to say, I assume Celestia would have used it IF her attempt to jog Twilight's memory against Discord had failed.) The second I saw that time travel episode, I was like "Oh crap." because I knew that it would add a new layer of complexity to any realistic fanfiction I tried to write, in the sense that I would have to come up with some way to write it off. I am not smart enough to deal with time travel. I am nowhere near smart enough. As HPMOR points out, even stable time loops are ridiculously complicated and drive people stark raving mad with regularity.