Concerning the sith classes, not having the military side of the sith empire would be a loss in term of story, so there would either be the trooper or the officer.

Having the officer, so being a leader could lead to interesting choices story wise. But I fear this class would be lacking in term of gameplay so let’s take the trooper instead but it’s already on the republic side.

So I guess that what Bioware will do is merging the officer with the Sith trooper to give it better armor and a good look (imagine a bike trooper with an imperial cap) that would satisfy sith trooper wannabes and differenciate the class from the senator (given it’s the last republic class) by improving its combat skills and survival at the expense of the effeciency of its buffs plus that
would be a sith class that uses cover.

My other bet for the sith is the spy, he could use cover and bushes to hide and disguise himself as an ennemy sabotaging by placing traps and ambushes, definately a good potential for story and gameplay.

Yet, concerning the senator I completly agree that it’s the last iconic possibilitie. But gameplay wise, apart from the buff role, I’m affraid that it would be to much like the smuggler using cover and spray and pray tactics.

Anyways I’m eager to see what Bioware has for us.