3. Victor Zsasz
Why: When Batman was first introduced, it was as a detective type. In a way the character has always maintained elements of this; some spying in Batman Begins, some clue finding in The Dark Knight. But as of yet, we really havent seen that side of Batman flourish, and Victor Zsasz would be a perfect channel for this revival. Imagine this; Batman on the hunt for Victor Zsasz - an out and out serial killer who we already knows exists in this world as he turned up in Batman Begins. Rich boy turned tramp, he gets a taste for killing after turning the tables during a street robbery. The gritty realism of a serial killer stalking the streets falls well into Nolans previous works of Insomnia, and the washed up investigator has been touched on with Memento. Zsasz marks his skin with a notch every time he kills, and although this all sounds more David Fincher than Christopher Nolan, it is easily within the directors capabilities to make this work. With the increased dark tone between Batman Begins and The Dark Knight, the inclusion of Zsasz could definitely dim the tone even further.
How: When Gotham P.D struggle to catch a killer who has the city gripped in fear, pleas ring out for the return of Batman. It would provide a great departure from the story of The Dark Knight, and provide Nolan with a great excuse not to address the absence of The Joker. A drawback comes in that Zsasz is not necessarily meaty enough as a villain to command an entire film, so he would need to be supplemented with a second baddie; or at least have a unique enough twist on the whole serial killer story arc. There is potential that Alfred could be killed, pushing Batman into darker territory, or maybe even give Zsasz a Joker-like mania with plans to release the tenants of Arkham Asylum. In the comics, Zsasz has some connection with Jeremiah Arkham who turns out to be the second incarnation of Black Mask - so there is your second villain right there.
Who: Sean Harris. Just look at the man and his resume. If it wasnt for the fact that he responds to the phrase thats a wrap, youd assume he was an
actual psychotic killer. Plus, he is a damn fine actor. Tim Booth, lead singer of the band James played the character in the original film but he would need to be re-cast for a part that required a speaking role.