Maybe have him, dunno, seeing QGJ’s body, sighing and leaving to go into self-exile. Then it would actually be dramatic to see him the next time when he’s turned, albeit ambiguously of course. That would present further problems because we would need to be introduced to him earlier in Episode 1 or at least hear his name so we’re like “Oh is that that dude?”
That’s actually exactly how I’m trying to do it. I’m trying to cut to Dooku sighing and leaving, just before cutting back to Windu and Yoda talking about the whole “master and apprentice” thing, which now has a double meaning with QGJ and Dooku.
The problem isn’t so much inserting Dooku into the film as it is finding the right frames of him to insert.
I’ve also considered trying to fit him into one of the Jedi Council scenes, but I’m not sure if I like that idea just yet.