Has anybody considered the possibility that he's playing someone from canon who didn't show up in TOS, or who was in TOS but wasn't a villain?
Considering it *right now*.
It seems to me that the whole point of an alternate timeline was to play with new and interesting "what if" scenarios.
It would fit with why they're being so tight lipped. Because the villain is going to be a total shocker. Khan wouldn't actually surprise anyone, they've been talking about it being Khan since this film was a twinkle in its daddy's eye.
Another thought I've had is that the villain is not actually seeking vengeance on *the Federation*, but is perhaps a Federation loyalist who has gone *too far* against some other enemy.