But it begs the question why was he impersonating a Jedi to begin with? He wants Obi Wan to join him, but for what purpose? His reason for trying to convince Obi Wan he's good and that together they can "destroy the sith" is never explained or followed up on. It just shows that George wasn't thinking at all about the characters' motivations when he wrote the script.

That's why, IMO, it's better to make him a rogue Jedi. It's not perfect that way either, as even then, the Jedi refusing to believe him when "he couldn't assassinate anyone. It's not in his character" is stupid.

Unless we can find a way to either give Dooku motivations that make sense for wanting to appear good (but really being evil) or make it more plausible that the Jedi don't believe him (has he tried explaining things to them? What reason have they possibly got to not question everything when he's TELLING them that he's discovered the republic is under Sith control?)

If these things can't be addressed whichever way an editor goes with it, I fear that the prequels will be forever broken.