I wouldn't mind a Croc who's surprisingly self-aware and pretty cunning as a main physical antagonist. I hate the idea of him being completely stupid; he should know he's not any smarter than his bosses, but it would be cool to see him have some common sense whenever Batman shows up. I figure he should be a freakishly strong warrior with major mood swings(probably tied to Hugo Strange in some way), but also a guy with some professional codes that he tries to follow.
Think of Deniro in Heat, but bigger, much less educated and a guy who likes working with a crew of loyal friends. And if anyone of them betray him, he'll rip their ******** heads off and beat them to death with them. Keep his new 52 hatred of substance abuse (again, think Hugo Strange), and make his more animalistic side a definite anomaly. This is the guy who bit off Officer Cash's hand, but this is also a guy who prefers to wear nicer suits and to have you mind your own business when he's around.
And make sure he sounds like Tychus Findley.