Also how about the Crystals 'choose' their owners. Hence why perhaps the two crystals amongst the beast tribes switch, as it selects a keeper/holder instead of it being chosen.

Thus you therefore should assign powers after you see the characters of the people. That way you could maybe match them up better to suit the story.

*Also willing to be a keeper.
As for the beast folk, would they also have a 'humanskin' a sort of way to interact with the humans/elves through that more humanlike form?