I'd like to see the races currently within the game playable, though I would like to see some non droid novelty pets for example hoojibs or ysalamir.
I'd actually like to see Ysalamir and more especially their racial ability..... it is quite a nice one that could really put an annoyance factor into those force using classes. Or even to just have one as a novelty pet.
http://starwars.wikia.com/wiki/Ysalamir
For anyone who doesn't who Ysalamir are a lizard like race which has the natural and constant ability to negate any force ability which is used within ten meters of them.
Hoojibs on the other hand are telepathic rabbit like creatures who have a tendency to feed on energy.
http://starwars.wikia.com/wiki/Hoojibs#Appearances
Why Bioware decided to not make Wookies playable I have no idea.