No, I don't want Khan to be a villain again. Make him a hero. Or, well, at anti-hero.
Are we forgetting what Khan was like when he was first alive? He was absolute dictator over 1/4 of Earth. His kind killed millions. They openly advocated the genocide of anyone who wasn't an Augment like them. And we're talking about making Khan the fucking HERO?
Compared to Khan, Admiral Marcus was Mother Theresa. Marcus was no hero, I admit, but neither was Khan. As a dictator and a murderer, Khan was worse than Hitler, Stalin and Pol Pot put together.