Am I missing something, but wasn't the "Dark Knight Rises" a comic in where he was an old man that fights and beats superman and .....dies?
I think the name is rather off. Someone has to fall (in comics) before they rise when they have already, for the most part, risen......
I think that they could probably still do well with a super power or two. Clayface would make an interesting foe, and you would not be forced to keep any actor on to play him!
Crock is the other, but I think Clayface would be the one that would make the most interesting plot.
Poison Ivy is another, and lets not forget Raj al Gul? (sp).
The thing they should concentrate on, though, is cameos. Hint that this is part of the DC universe. Show superman flying by in the background, but do not make it obvious. Show Lex Luthor, or the Flash, or Aquaman on a monitor in the monitor array in the Bat Cave, doing an interview on CNNN, but do not put them front and center.
Some things they get right in these movies, like setting up the doctor in the spiderman movies. You KNOW he will become the lizard, but it works much better on a character you know than one they have to set up at the start of the movie because it is the first time some people have seen them.....