- Black Mask could work as the mastermind, sending folks after Bats while he tries to reestablish an organized crime foothold in Gotham. Might be a good way to sneak in Rupert Thorne from the animated cartoon from the 90's.
Done right, Black Mask could be pretty awesome. Crazy, but also a horrifyingly intelligent and machiavellian crime lord.
- Bane could potentially work as the main villain, but only if they actually portray him as intelligent for once.
That's a real big if, only because Hollywood is not so fond of the intelligent muscleheads. Plus, you run the risk of half the movie being about Batman fighting his addiction to the Venom drug.
- Mr. Zsasz would make a great henchmen or lieutenant. He could work in a manner similar to Killer Croc.
He was in Batman Begins. Batman pantsed him en passant.
- The Ventriloquist would be another great opening foe, but only if they really play up the insanity and don't make Scarface look ridiculous.
They'd have to practically make him the Jigsaw Killer for this to work at all. Not saying that can't but it seems a long-shot.
Other possibilities:
-The Black Glove + allies. A bit recent, but I thought the whole concept was very well done.
-Amanda Waller (as a B-plot character, anyways)
-Lock-up (as a B-character)
-Lady Shiva (that could be fucking awesome)
-Talia al Gul would be hard, but you could have an awesome tragic romance story going on there, and we could finally forgive Nolan for leaving her out of Batman Begins and inventing a reason to have Katie Holmes in it.
- David Caine (B-character, cool as he is, he doesn't work so well without a boss behind him)
-Some other take on Azrael, using the centuries-old order of papal assassins background that they gave him when he got his own comic.
However... looking over the previous two Batman movies, what would I really like to see? A Gotham Central movie.
QFFuckingT. That would rock so hard.