What if Krall's people are uber xenophobes that have been destroying any alien ship that comes close to their territory, not just for years but decades.
Then it would be logical, ahem, that the crew would have to deal with a multicultural mix of alien survivors, perhaps providing the leadership to band the ragtag group together..
From what Pegg said last year, it does now appear STB is perhaps a heist film populated with Star Trek characters.
The crew are split into 3 groups (Kirk, Chekov & Scotty; Bones & Spock; Uhura & Sulu). Each perhaps having a piece of the jigsaw puzzle. What they do, the alliances the forge, etc allow them to complete their tasks ie, pull off the heist.