4. Alberto Falcone
Another core component of the Batman mythos Rocksteady are yet to implement into their main trilogy is the existence of the Falcone family. Sure you could introduce fist to face for many of Falcone's men in Arkham Origins, but he's nowhere near such an integral part of the story as on the silver screen or even Scott Snyder's ongoing Batman Eternal arc. His brief appearance in Origins is short on content but leaves open a lot of potential, as the theory goes after witnessing what Batman can do to his foes through fear and intimidation, a young Falcone becomes hell-bent on enacting the same sort of punishment to Batman. Training himself over the course of the many years between Origins and Knight (about eight if speculation is correct) it would take Alberto to the right age for the part, and with him having ties to the Falcone family he's got just the right amount of tie-in credibility to make for a really believable candidate - especially since Rocksteady announced they consider Warner Bros. work on Arkham Origins to be canon with their own.