Well, I can tell you that the Kzinti are out due to rights. The Bynar are probably out due to their paired status (you'd have to have two characters... which might be interesting, but very difficult to pull off). The Edosian are probably out since they're tripedal, which would pose issues with animation, clothing compatibility, and stuff as simply as sitting in your captain's chair.
Ktarian could happen. Anticans too, in fact I've been saying since beta that they'd be a good counterbalance to the Caitians. On that note, the Selay would probably be a good option as well (if they can figure out how to fit those necks+hoods through a Starfleet or KDF uniform's neck).
if you ask me we can keep on waiting for them. Talaxians is stretching it a bit as to why they would be here, but at least they look interesting.
androids and holograms look like humans. you could make convincing versions in the tailor, same with cardassians, and a smooth headed romulan. add that romulan head ridge and we can make them too. they are basically boring additions. you can't make anything that even looks remotely lurian.
xindi i would agree with adding as they are again very interesting visually, although i get the feeling they wont be along until they feature in a weekly series.
Smooth headed Romulan, bah! The Xindi Primate option with only one bar active on the slider plus a bit of addage to the brow protrusion makes a fine Romulan.
And my opinion for one of the coolest race, the Chameloid. Like Martia from "The Undiscovered Country". Shapeshifters, made one just recently using the alien tailor tech. Using my like eight other costume slots as seperate forms.