I'm unsure if there are any plans for this, but I do think it'd be interesting - would probably be something only added super late though, realistically, but their fun to think about
I'm imaginging, say
Bec Noir: I imagine he'd move and fight sort of like Street Fighter 2 Akuma, plus teleporting shenanigans
The Condesce: Both to pay homage to Collide, but I also think she'd play like MK2 Shao Kahn
Lord English would make sense for a final fight: IDK if it'd even be winnable, but the concept would be cool. You could even make it say, a two stage boss. Like, first you fight Scratch, then he ends up breaking out into English like in the comic
Just some off the top of head ideas

Imagine if you will, Jasprosesprite^2 as a boss and unlockable character, her entire gimmick is that she's just Neco-Arc Chaos from Melty Blood: Actress Again Current Code but she's B tier instead of F tier
Good D4y