I would absolutely love to play a little moogle, but their anatomies would probably make it very hard on the design team to make gear for them.

People say it doesn't make sense lore-wise as well but I disagree with that point personally. For all we know the dev team in-charge of the lore could make it so for one reason or another, Moogles have decided to join us in our adventures and the expansion can even be centered around them (like how HW is centered around dragons).