Elias Vaughn - Hmm. Connery without the Scottish accent, I suppose. Except, what's the point of an accent-less Connery?

Possibly Edward James Olmos.
Prynn Tenmei - It's
got to be Grace Park.
Shar - Vincent Kartheiser of
Angel fame. The guy can act, and he's effeminate enough that I can buy him as a
chan.
Admiral Akaar - Hmm. Tough one. I honestly can't think of many incredibly tall character actors. Any takers?
Taran'atar - Ah, c'mon. After he's been a guest star so often, let's go ahead and give Tony Todd a regular role.

To expand things, though, I find that the voice of Taran'atar in my head also resembles somewhat that of Laurence Fishbourne.
Sam Bowers - Hmm. Jesse L. Martin works, though I think Bowers is supposed to be a little bit younger than that. Matthew St. Patrick of
Six Feet Under fame also comes to mind.
Phillipa Mathias - Mary-Louise Parker (of
Angels in America,
West Wing, and theatrical fame). Just because we need an excuse to bring her aboard.
Treir - I'm tempted to typecast Cyia Batten as Treir, because she did an excellent job in a very horrible episode of ENT as Navaar. Suzie Plakston, of course, also comes to mind, though I think Treir's supposed to be younger than that.
Hetik - Give it to Nick Lachey. What the hell, the poor guy just got dumped, and he's certainly himboish enough.
Cenn Desca - Liev Schreiber, who played John Clark in
The Sum of All Fears comes to mind, but I honestly can't recall what Major Cenn is supposed to look like. Alexis Denisof also comes to mind -- mostly because he's one of my favorite actors and I'd look for any excuse to have him aboard. He's probably got the wrong build for it, though.
Ethan Locken - It's got to be Anthony Michael Hall. The man did an amazing job playing Bill Gates in
Pirates of Silicon Valley; combine that with the darkness of Johnny Smith from
The Dead Zone, and you've got a great villain.
Mr. Cole - Also a tough one. Hugh Laurie, star of
House, MD comes to mind. Of course, Agent Cole hasn't reappeared since
Section 31: Abyss, so who the hell knows if he's going to be a major character or not?
First Minister Asarem Wadeen - Angela Bassett certainly comes to mind here. I might say Halle Berry if she was about ten years older.