This would be my dream come true (as I really want to play a sith Marauder that goes to the light) but I don't foresee it happening. Bioware spent over $500 million on the game already and the script is already longer than several copies of "War & Peace." A faction change would take way to much time and effort. Think about it: A change in faction would make your whole origin story and motivations different and would essentially be an entire new class story. Imagine if I were a Jedi Knight gone darkside. There is no way Darth Baras would treat me the same as some Sith pureblood. The only way this could happen is if 4+ years from now SWTOR is still going strong, made up the $500 million+, and Bioware wants to reignite interest in the game. Until then, I will be satisfied with my counselor, knight, Sith warrior, Inquisitor, Bounty Hunter, and Imperial Agent playthroughs.

In terms of sheer power, I'd say he pretty much maxed out (ignoring the idea he was enslaved to it, as all Sith essentially are). Besides eating an entire planet, he killed some of the most powerful Jedi, including master Vandarr and any other Masters that survived Malak's attack of Dantoine (exception given to the 3 that show up in KOTOR 2).

While I know that Flesh Raiders can become Jedi (who eat the flesh of sentient species) I think the sith are to corrupt. Their companion skill is punish, which I don't think would be tolerated by the Jedi. While it may be bad writing, I think there are simply no good sith as they are inbred evil incarnate.

To be certain, Shadows are not your standard tanks, but are excellent at stealth. After level 22 in which you can stealth out of combat, you can kill a person, run, and come back, until everyone is dead if you are really weak. I found that while one Jedi shadow may not be able to accomplish everything, 2 Jedi shadows dominate, CCing everything and stealthing through entire missions. Ultimately, a Jedi counselor class is a supporting character, whether as a healer Jedi Sage or a first strike and flee to the back shadow. Players must RP this aspect, and if they are not comfortable, should switch. Counselors are not for everyone, but once you and your friends learn how to use them, they are excellent.