On the other hand, Eliezer is much better at lacing in the didacticism since it feels like the lessons has for the reader are abandoned toward the end of book 1; and there isn't much one could learn from book 2 with Elspeth.

Where story and didacticism are in tension, I chuck didacticism in favor of story.

I came into Luminosity expecting Bella to sort of be like Harry in MoR; but she's not very much like him.

Well, good, I wouldn't want to be doing the exact same thing. How redundant. (Also, have to admit that while Eliezer's writing has many strong points, writing characters I'm interested in welcoming into my brain ain't among them.)

Harry with Bella's advantages and obstacles would have taken over the world in the first few years.

I think Harry would probably have gotten himself killed the minute he wandered near Volterra and was too obtrusively dangerous. Pretty much everybody who spends any amount of time with Harry in his story figures he's probably kind of hazardous to have around, even as an ally, and he doesn't curb this tendency very quickly. This is the sort of character trait that makes the Volturi kill you. (And had they earnestly tried to kill Bella in Volterra, even her juiced-up shield wouldn't have saved her. The fact that they were willing to risk waiting a while to see how she turned out allowed her to survive.)

Vampires die easily of fire? Splendid, Bella spends a few months reading and developing a fuel-air bomb and there they go.

That would be boring and tweaks personal buttons of mine. Sorry.

(Easily justifiable, too, consequentially.)

There is a sharp limit to how much this can really surprise you if you have been paying any attention. If you want to read stories where the Good Guys reason consequentialistically, find another author.