You have Lalafell, Midlanders, Miqo'te, and Au Ra for all your "I want to be the little girl" needs. Why do you need Viera to be short, too?

Also, the Feol Viera are not "smaller and thinner" than any other Viera. That's misinformation from a fanmade picture and not part of the story from the only game they made an appearance in, Final Fantasy XII: Revenant Wings.