As for changing race, assuming the change is to a playable race (as opposed to something think an Ancient Gold Dragon) and the character loses their original racial benefits, I would allow it without risk (though it would have the 33% chance and weakness).
I'd say changing race is just replicate the Reincarnate spell (a lowly 5th level spell). OK, you get to choose the race, but it's not important if cast during downtime since you can recast the spell every day until you get your favorite result). Since it would be replicating a spell effect, it wouldn't even incur the penalty.