This might be nuts, but could Jon Hamm have pulled it off?
And I had to go look this guys name up, but wouldn't this dude have been an awesome 'older' batman as well?
Joe Manganiello (I don't know if anyone would've recognized the name). Dude's already built like a truck and I think he was in Spiderman, so it's not something he's unfamiliar with.
Affleck? Suck pick. Even if Hamm couldn't have done it, Manganiello would've killed it.
EDIT: I see I Q'd the Jon Hamm suggestion.