these are the criteria devs have mentioned in previous talks about new races
1. Must speak basic (most of the species not just the one off's here and there)
2. Must fit in all existing cut scenes (this is why Wookie, Jawa, etc won't be playable race)
3. Must be able to correctly equip most existing armor sets
4. Must be romance-able (in other words, their face needs to have a humanoid appearance for romance scene