Based on some 'Characters in one property teach another to be like them' twinning tf idea I had, and some neat fanart some of the crew of Helluva Boss posted, I wanted to do these transformations:

Mari Makinami --> Sallie May: An odd choice at first, but probable the most 'fitting' for personality in a way. Motivated by some fanart of Sallie in her plugsuit and my love of both characters boiling over.

Asuka Shikinami --> Stella: Princess into 'Queen', a lovely case of making those red flags bigger and worse (as well as her drumsticks). Could be fun playing off Stella's arrogance about making this annoying human better against Asuka's resistance to being turned into awful(ly hot) MILF from hell.

Rei Ayanami --> Verosika Mayday: Another weird choice, but playing to my type as making Rei some kind of ultra kinky gal that's all in on proving that fact works well here. And having her try and be 'proper succubus' while still retaining Rei-isms afterwards sounds like a lot of fun.

The play off as past rivalries flair up again with new demon hormones and drives would be sweet as well. (I'd probably do another 'post Eva 4.0' thing so it's just utterly incongruent transformation weirdness in an otherwise mundane world.)

Poor Shinji would just have to deal with his girlfriend turned imp and the sudden hell harem competition that seems to have been set off around him I suppose.