Well earlier I suggested giving Ryu a Ken and Akuma mode (like MVC2) and maybe a Sakura mode. How about giving Morrigan a Lilith mode? Her outfit would change colors, as well as her hair, and then give her the moves and abilities of Lilith.
Well that may be too much work, ideally there would be some shrinkage in the chest region, and her hair would be much shorter too. Just changing hair color and outfit though, doesn't really require much.