One thing that occurs to me is that Nolan tends to cast his villains quite young. I don't think anyone would have anticipated 20-something actors like Cillian Murphy or Heath Ledger - each of them younger than Bale - as Scarecrow or Joker. Even Liam Neeson was relatively young for the role of Ras, while Aaron Eckhart was younger than Tommy Lee Jones or Billy Dee Williams (though Harvey in the comics is usually a near contemporary of Bruce age-wise). When Empire recently discussed casting prospects for the next Batmovie, they suggested Casey Affleck for The Riddler. Given the acclaim he received for ... Jesse James (an Oscar nod for the latter, IIRC) and Gone, Baby Gone, he might be in with a chance.