Well, they should all virtually stay how they've always been. Mr. Freeze gets an update with a cooler and more efficient suit, but nothing too weird. Bane is good as he is. Joker and Two-Face you can't mess with. CLAYFACE is one I'd like to see on stage, he'd be cool, just don't make him a dripping mess. Everyone virtually should stay the same as they've been throughout the years, I don't like drastic changes, and I don't think anybody would like it if you saw say, Firefly, wearing a speedo with enough chest hair to shame Kraven and piercings all over his body, know what I mean? You gotta keep them the same, and make minor changes.
Hopefully when Scarecrow gets the big role in the future, he gets to dress up bit more of a scarecrow than just a burlap mask.
Two-Face: his face needs to be really damage instead just a plain red makeup on his face. If you guys seen "Constantine," that guy with the silver coin has the exact look of a Two-Face that I can picture in a movie plus red favor to it.
Catwoman: exact same thing as the one from "Batman Returns," but I don't mind her wearing a big eyes goggle like in comics. She's still sexy in leathers.