Besides the list we have the photos of Cumberpatch in Starfleet uniform, with human ears and forehead, making him a human, or human lookalike. So he's not a Horta, or Talosian. I suppose he could be a Q, but that race isn't established in J.J.'s alter-verse. So, if its one of those "named", it can't be Mudd, who dresses like a gigolo, or Trelane, who dresses like Liberace. It has to be Mitchell.
On the topic of villian, Peter Weller plays a villian in the movie according to this, http://badassdigest.com/2011/12/07/p...y-be-revealed/