Originally Posted by omegaman
In my opinion… Marcus didn't need Khan at all. He could have simply loaded the photon torpedoes on the Vengeance and carried out the mission himself in complete secrecy, leaving Kirk to be the fall guy when the Klingons came looking… like in Star Trek VI: The Undiscovered Country.
I think he wasn't looking for a fall guy, he was looking by that point to clear up all his loose ends whilst also getting his war.
Loose ends can talk and investigate (which kind of undid the plan in The Undiscovered Country
..................well that and their plan didn't seem fully thought out either!) the things their left holding the bag on.