Where the heck did this idea come from that you need the Dark Side to see the future? Heck, ALL Jedi have a limited sense of the future! This is a nonsense idea.
The closest I have heard to it is that Dooku had a particular talent for future sense, and of course Dooku is a bad guy. But there is no DIRECT link between the two.
Meanwhile, a true traitor in the JC is unlikely, Windu's line in 'Choices' still confuses me, and you can make up any reason at all (within reason...) as to how the ship in TPM was traced but the fact is the film SHOULD have told us.