I do not see this being that hard to implement do to the fact the species is already in the game look on Taris and i believe the trooper gets a Cathar companion so the only Technical reason why it would take awhile to Implement is because of the voice over and story line that would need to be done and created to implement into the game.
The voice work varies by class and gender, not by species.
The only work necessary is the design of the skins for the models. A few Cathar are in the game already, but there aren't enough to probably cover all of the standard customization options people will expect. The skeletons are the same for all species, and the animations are tied to the class alone, so no new work there.
Personally, I have no interest in playing one, but I do find it remarkable that with the number of people who have asked for them, and the apparent simplicity of just recoloring some skins (which they are so good at) that it would take so long to implement something initially claimed to be in the works a year ago.