I don't think the producers care about the the ethnicity of the actor playing Khan as much as the fans, they will hire the actor they like the most. And since Khan was a genetically engineered person he theoretically could have any kind of look.
As far as resembling the original actor, Cochrane in FC didn't look anything like the original actor and that wasn't even an alternate timeline. Also in this alternate timeline Kirk has blue eyes.
Yeah, it would have been better to cast someone who reminds us of the original Khan, but hopefully the performance is so good that will make it worthed..