Yep, Two Face needs a gang, and they should be scared to death of him. Imagine working for a man that looks half-zombie, and who makes decisions effecting your life and livelihood on the flip of a coin. What would prevent you slipping quietly away? It has to be the knowledge that you might come home to find him flipping that coin, standing in the ashes of your burnt-out house.
I don't know how feasible or well advised it would be to try to work in two-themed crimes, but the way to do it might be to simply have Two Face's gang always commit two separate heists/hits/whatever simultaneously, stretching Batman's ability to predict their targets or to intervene.
Whoever plays the part is likely to also be a candidate for Bruce/Batman. Although he hasn't had a stellar movie career, I have a notion that Jonathan Rhys-Meyers could play the part very well. His venal, mercurial and conflicted performance as Henry VIII in 'The Tudors' was quite compelling (though his attempt to suddenly be 20 years older was terrible!). He starred opposite Henry Cavill.
He certainly has that Appollo/pretty boy thing.