With the concept of a Knight, the potential for LS/DS is also there. (There are robes for Jedi Knights and Dark Jedi Knights respectively)
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And don't forget the whole concept of of a knight, without being a "knight". Like the old "Prince & The Pauper" story, where the prince pretends to be a pauper and yet still comports himself as a prince must: that can be applied to a knight just as well. In other words, the characteristics that define a knight can be expressed by someone who has not been officially recognised as a knight, and this may be a good knight or otherwise (Black Knight, anyone?).
What are you asking? AFAIK (admittedly not much, and all of it based on the loading screen ticker tape from K1), the "Original Sith" were some sort of insect-like beasties. Are you suggesting that these beasties should be enemies, playable characters, or both?