1, I would rather the in-game lore/culture representations be fleshed out for the existing clans before we got new ones. (like moonkeepers and duskwights have been in the game since 1.0, and if we get a new tribe of dogo'te or, idk green elves before we get a non-fatemob representation of either, it would be really aggravating.) Plus, there's nothing a new clan wouldn't add that couldn't also be added to the existing races as more options.
2, easiest way to add garleans into the game is to just add a garlean eye headpiece to the gold saucer or like a drop from the lowest level garlean fate and let people make hyurs/short-eared elezen to kinda fake it for their RP.
2.a, or, hear me out, garlean beast tribe reward. :>