Taylor and Altpowers Advice
I guess my biggest piece of advice is that the ability or superpower doesn't make for an interesting character. Basically, if you take away the powers, are you left with an interesting character? Canon Taylor is definitely one such character. Most fanfic Taylors, not so much.
In canon, the powers are a tool used to explore what kind of person Taylor is. She gets to use bugs and insects and has to find creative ways to make due with that in a setting where plenty of people are well defended against it or have no defense at all and how she balances that ability and that perception on her. It's all about giving her options and restrictions. When she uses it and most importantly, when she doesn't. Taylor doesn't take it out on her bullies in any way shape or form, even though she could get away with it very easily. That says a lot about the kind of person Taylor is. She also later on uses her powers to carve our someone's eyes and rot off Lung's crotch.
Those two aspects, of not harming the defenseless and civilians and also going all out against dangerous, vile criminals in extreme situations are what defines Taylor. Taylor is seen as this vicious, creepy and monstrous cape at some point, simply because her ability is conceptually horrifying. Very few people can handle being swarmed by insects and spiders. It's traumatizing by nature. Barring the very few people who can survive an all out assault with them like Lung, most people won't walk away from countless wasp stings and poisonous spider bites and Taylor has to be creative on how to use them in order to not kill anyone. Or with Alexandria, how to use her powers particularly ruthlessly in order to harm someone who can't be physically harmed.
All that works because Taylor is the kind of person who would do all of these objectively horrible things to other humans but she also needs a good reason to do so. Panacea has arguably one of the strongest powers and you can find a lot of stories where a Panacea with a different mentality and less ethics can do wonders with it, missing the point of Panacea who is, as a person, uncreative and bound by self-imposed rules and restrictions. She simply won't use her abilities to their fullest potential until she changes a lot and even then there are a lot of limits. Taylor as a person is someone who can get a lot of mileage out of anything as she is creative, brave and ruthless enough to come up with things under pressure. Give her any power and she would shine, which is part of the appeal as to why there are so many altpower Taylor fanfics.
Wildbow recently posted Amy joins the Undersiders snippets and those were certainly not happy ends where Amy’s incredible powers had amazing synergy with Taylor and co. Their powers might be compatible but the personalities are definitely not as too much bad blood existed between them and an allegiance of convenience between horribly traumatized teenagers in horrible situations where one party really loathes the rest can’t be anything but a recipe for disaster, no matter how well the powers combine. They are people first, with different goals, values and personalities and powers distant second.
Most alt power fanfics, though, waste a lot of time exploring the powers, what they can do, and how amazing they are and how far reaching changes they can have, when it should be about Taylor and the hand that those powers give to her. There are no training montages in canon, on how Taylor tries to practice with her powers. At most we get her trying to weave the costumes or collecting bugs in preparation.
If you can do something similar with whatever the alt power is, awesome. If it's just Taylor building something awesome, then stomp whoever the villains are and then have PHO and whatnot marvel at her cool powers, less so.
At least my thoughts on it, as always, feel free to completely disregard any and all of this.