1) Well, I went and did that, and it narrowed it down from 24 to 12. I suppose hat's an improvement lol
2) That's what I usually do, and I only really go for wacky shit when I get bored. This is what lead to me thinking I might be able to trick myself with a harder character, since I sat there doing Naoto's dash cancelling till I got it down semi-consistently.
2.5) Again, usual stuff for when I'm learning a character. I do have a thing for long ass pressure or stagger pressure.
3) I feel like I do a lot more research than is expected of the normal person when they're picking up a character, since I'll sit there and watch hours of gameplay for a character I want to play. Hell, I'll make mental notes of stuff for characters I don't play on the off chance I'll pick them up eventually.
Most of the aesthetics/personalities determined the characters I'll never play, and that's pretty much been set in stone since CT/whenever the character is introduced. I think me being an extremely flexible player kind of screws with taking things out based on playstyle, since I can go from playing something like Nu to playing someone like Azrael pretty easily. I don't think I have a specific preferred playstyle.
With the list thing, I ended up with Hakumen, Nu, Hazama, Makoto, Relius, Azrael, Kokonoe, Naoto, Nine, Izanami and Mai, and I can't really think of a reason to take any of them off besides silly shit. I could probably add Izayoi to it if I actually played her, but I never got around to it. Also, if there's some kind of playstyle correlation you can see that I'm blind to, I'd love to know for future reference.
Since you cut the list of characters by ~60%, I'd say you did help.