^As I've said, I really, really do not think their motive in casting Cumberbatch was to favor white actors over nonwhite ones. In fact, Orci has pretty much confirmed that they were trying to avoid the racial stereotype of the dark-skinned terrorist. So I think that in trying to avoid racial discrimination in that sense, they accidentally stepped into a different kind of discrimination quagmire. Good intentions leading to an unfortunate result.
I think part of the problem is that they're hamstrung in casting a lot of roles due to the conceit of this being an alternate timeline rather than a pure continuity reboot. Comic-book movies are free to change characters' ethnicity and correct the white dominance of the past (or replace Jimmy Olsen with Jenny as Man of Steel did), but these guys are stuck when casting roles like Christopher Pike, Carol Marcus and her father, and the like, because the alternate-timeline premise demands that they bear a resemblance to the originals. If that weren't the case, then maybe the casting of a white Khan/Harrison could've been offset by casting the Marcuses differently, or casting Pike differently in both movies. Heck, with a wholesale reboot we maybe could've had, say, a black McCoy, a female Sulu or Chekov, maybe an Indian Scotty (there are lots of people of South Asian ancestry in the UK). But as it is, they're kind of stuck with the racial and gender biases of the original series' casting, and thus can't be as progressive as Bad Robot has been in several of its other productions.
Even though I thought the alternate universe idea was and is a brilliant way to tell new stories while not completely eschewing the Prime Universe that I grew up in so to speak, I think that a complete reboot would help avoid some of the problems that this new iteration of Trek has run into.
As for Khan if this had been a complete reboot, I likely would've still grumbled about Cumberbatch being Khan but would've found it more tolerable since he isn't supposed to be the same guy that Montalban played. And I do think the idea of mixing up the races/ethnicities of various characters as offsets could've been intriguing to see. Who knows if I would've agreed with all of the changes but I would've been willing to see how it all came together.