Khan was wasted, but I think they did it like that on purpose to save him for a return appearance. Personally, I thought he was unnecessary and that people like Cumberbatch and that his character name is irrelevant. I would have preferred him to be an original creation. Honestly, they barely get into his backstory because it's dense and geeky and hard to explain. So why bother? Why couldn't he have been John Harrison, a victim of Admiral Robocop's attempts to wage war? He could still have been genetically augmented. Honestly, his augmentation was purely physical anyway. Khan deserved to have the movie to himself. Harrison is fine as a patsy. And really? Khan designing weapons? I can't believe Marcus wouldn't thaw out Khan and create an army of genetically enhanced warriors to fight the stronger Klingons. Couldn't anyone on Earth have designed a ship or torpedoes? Who goes to a guy from 1993 to do that? Would you resurrect Einstein and have him make an iPod app?