Fair enough, but I'll take acting ability and screen presence over... height requirements, any day. Didn't know Foxx was 5'9". Not an ideal for Bishop but if you want to get technical then the actor shouldn't be black at all as Bishop is aboriginal - Marvel simply portrays him as a black man. And no, I don't extend the classification of "black" to any brown skinned person with similar attributes as those crackpots over on CBR. Sorry I went through that insulting over there.
Anything thing we've gotten on film is an adaptation not a carbon copy. Sometimes they hit the nail with dead likeliness as they did with Pat Stewart, Ian, and Kelsey Grammer but then you have departures like Hugh's Wolverine and Josh Brolin's Cable that work out legendarily. I wouldn't get too held up on this because I guarantee you the MCU version of the X-Men is probably going to upset you.