I was worried about it being a huge mess, at first, but putting them out in the open will allow for more criticism and dialogue, so that was a mistake. I was a bit tired when I posted that comment. I'll post your comments here then.

These ideas are courtesy of MixedNuts, please give him the (+) karma and not me. I'll take all the (-) karma.

• Limyaael's rants (and everything else on that site).
• Think about where she got her ideas from. In the movie everything stems from her humanity hobby and her teenage rebellion against her helicopter dad (who is overprotective but not evil; upping the bigotry sounds worthwhile but making him not genuinely concerned for her well-being sounds like a loss of complexity). If she's going to have any explicit feminist ideals, why? Did she come up with them herself, or is there a feminist movement, or is she part of a different movement whose ideas she ran away with? Is that movement old, with several waves, or just finding its voice? How divided is it? Is she concerned about straightforward rights, first-wave style, or is she getting into the philosophical significance of gender roles? Is she selfish, as in the movie, or concerned about helping other mermaids/human wannabes/females of all species? How does she relate to her sisters, and other people who tell her "I don't want to be liberated, thank you very much"?
• Intersectionality: is she all about feminism/humanity/whatever she stands for, and if so does she try to make that work for all mermaids, or does she conveniently forget that not everyone is a sheltered princess with no responsibilities other than an occasional concert? Or does she fight for other causes - because she needed to make accommodations for non-princesses, or because she has a general philosophical system she noticed applies elsewhere? If so, what does she do about, say, the absolute monarchy? (Mad props if you dissect the class/race implications of Sebastian's Under the sea attitude and include the blackfish.)
• How is society for people who are neither royalty, working for royalty, or evil mages, anyway?
• In the movie, she's hopelessly naive about humans. In particular, she thinks human women are much freer than mermaids, and it doesn't really hit her that they don't know fish are people. Does she start out that way, and if so what happens when she learns it? Once she knows it, what does she do about it? Does she genuinely care about understanding and helping humans or does she just go "ooh, shiny"?
• How alone is she? In the movie, her sidekicks don't share any of her ideas and are pretty much incompetent. Does she look for better allies? How does she value cooperation relative to personal friendship?
• Where does she stand, on the diplomat - firebrand - murderous fanatic spectrum? Does that change over time, and why?
• Does she have to be straight? (Limyaael's campaign for asexual female characters has gotten into me.)
• What's the relationship between Triton and Ursula, in terms of power imbalance, current truce (if so) conditions, ability to destroy each other if they sacrifice everything for it and conditions for being willing to do so?
• What do her sisters want? How do they feel about Triton, about society, about Ariel being the favorite, about Ariel's weird ideas, about Triton's reactions?
• What's Ursula's backstory? How and why did she learn magic? Why does she use her powers for this specific job? Does she really believe her "but all the while I've been a saint" claims (there's some possible commentary on "People should be able to sign any contract including leonine ones"-brand libertarianism here), or does she use that to fly under some legal radar, or to ensnare her victims? How eager is she to drop the act (and if it's not entirely an act, how does she justify it) when convenient? Do her victims know that, and how does it affect their willingness to do business with her?
• Why do people defend a bigoted society? Some major villains can just be evil, but a whole society can't; they must have reasons that sound good from their perspective, possibly with complex justifications.

Mostly Disney, but I might borrow things from HCA.

Your link just led to an Aladdin icon, so I assume you had something else in mind.

When I was rereading the thread, it also occurred to me that Ursula was the hard part. My take is that she's what she is for much the same reason crime bosses are what they are-- power, safety, and excitement-- with the last two having to be balanced. It might be interesting if there was a family tradition of being outlaw magic users.

However, I'm not a feminist, though I agree with a lot of feminist ideas. I think men and women are fairly similar, and that means some women are going to be very bad news. I'm inclined to think that the status differences between men and women have a lot to do with men being (for reasons that aren't clear to me) better at group violence. It's not about the upper body strength.

Ursula could be an outcast from her own society because she's mean and irresponsible. You could spin a story about her which goes either way-- the octos are actually dominant (or at least secure/isolated), and they exile their criminals who then predate various cultures the octos don't care about.

Alternatively, the mers dominate the octos, and Ursula has ambition and no place inside respectable mer society to use it.

Real world octopi are short-lived. How would that affect their approach to prisoner's dilemmas? A claim that they're unreliable because of their short lives could also be used to justify prejudice against them.

However, I'm just noodling here-- I've only seen the movie once.