(I don't have a dedicated GPU at the moment, so it's gonna be just a theory from my part...
)
How viable do you guys think it might be, the idea of a style transfer of sorts that helps "converting" a character's sprite (individually, or a full sheet) into another one with a similar style?
Y'know, sorta like this rough illustration: detect the shapes, then change the shading and, if possible, some of the proportions as well;
I'm aware that the current A.I. tools might still be kinda wonky, when it comes to pixel art. But even a result that is similar enough to the desired style could still help speeding up the workflow of a full sprite sheet by quite a bunch, perhaps...?