Double post =/
But might aswell use it.
In relation to which villain to use, I say stay away from Mr Freeze, Poison Ivy, Clayman, etc, too supernatural.
Riddler would be absolutely PERFECT, with all the riddles and clues etc, could make a superbly clever film, like TDK was, and if anyone's watched the Prestige, will know, Christopher Nolan is damn good at that sort of thing, however, the approach could be a little too similar to the Joker? The evil genius characters are much better than the supernatural characters, so maybe even the Penguin? But perhaps without so many umbrella gadgets.