Ok, KingDaniel. But how would they explain it in a film? In ST2009 Spock Prime explained about Nero by vulcan mind meld and many people didnīt understand. Unless it has many flashbacks.
What needs to be established? Mitchell and Kirk were friends in TOS, they crossed the Great Barrier and Mitchell's eyes went funny and he got Telepathic powers. There's really nothing of Mitchell's history that needs to be explained, and they don't even need to make Mitchell and Kirk old friends.
He could just be sitting at a station on the Bridge without any introduction other than Kirk calling out his name and rank and asking for a status, and whatever causes Gary Mitchell to become the Villian happens.
My thinking is that if it is Mitchell, he'll be on the ship commanded by Peter Weller, and that's the one that is affected and causes Mitchell to turn into the god-like person.
I still think the movie will somehow draw from the book "Heart of Darkness", and it will entail Mitchell becoming like a god to an alien race, with Kirk and crew assigned to find him and stop him.