I keep going through characters from TOS, even the good guys, and Khan is still the only one I can perceive of as having enough name recognition to be of interest to a general audience.
But that doesn't mean I'm convinced he's Khan. If he is, he's going to have one hell of a backstory that led him to becoming Harrison.
What I'm holding out hope for is Harrison's true identity is a jaw-dropping surprise. An "ohmygodreally?" moment. Khan would be OK. But would that be a surprise? Not any more. At this point, it would be anticlimactic.
Completely agreed. Khan would make sense from the jawdropping point of view (although it wouldn't really surprise anyone anymore at this point), but storywise it wouldn't make any sense at all.
But who says it has to be someone well known to the general audience? Maybe his backstory will be explained in a few throwaway lines or in a flashback scene. But that still makes me scratch my head about who from TOS it could be. If it wasn't so extremely unlikely, I'd say it was someone we know from the (Prime)TNG era. Or maybe from Enterprise ... Malcolm Reed's grandson perhaps? Unlikely, I know.