I would agree that a montage would work best - Perhaps we see Gordon getting promoted or talking to Batman about his promotion. I can't quite articulate how this would work, but I'd like to see Bruce still struggling with whether or not this is the right thing for him to do...especially since Rachel could be dead and Harvey is now scarred. Someone mentioned him feeling like a failure (and I would agree...TAS captured that perfectly), and I'd like to see the escalation really getting to him. Perhaps he'd be sitting in the cave having those Nolan-flashbacks. We don't actually see the Joker escaping Arkham, rather you see a guard lying face up in the threshold of the Joker's open cell with a bloody smile carved into his face. Rather than have Harvey/Two-Face flip a coin to decide to do or not to do something, I'd like to see him flip a coin asking himself, "who should I off first...the bat or the clown?" He flips the coin into the air, catches it, flips it on top of his hand to reveal, only to himself, who his victim will be. Scene ends with him looking down, as a sick looking smile spreads across his gruesome face. Fade...to...black...
Just my ideas...