What Are The Old Republic's Three Final Classes?

Assuming that the Jedi and Sith will be two of the five unrevealed classes in Star Wars: The Old Republic, Massively speculates as to what the remaining three will be.
The last pairing really have been the most difficult to determine. For a long while I considered a pet class, but with the companion system it seems a little redundant. Instead, what finally dawned on me is that the likely solution is yet another blended class with many varying builds. I'll start with the Republic variant: the mechanic.

Decent with a blaster, but far better at field repairs and support, the mechanic focuses on many fields of utilitarian expertise. One such area would be basic astromech or protocol droids, while another could involve heavy crowd control through various pieces of deployable equipment like turrets, or cover for the classes that can use it. As BioWare has hinted at in regards to high-level PvP and mission play, the mechanic would have the option to invest in healing and buffing abilities, as well as some de-buffing. Come to think of it, this is essentially the iconic Chewie class.