I'd personally go for the Barbary Trio. I think it would be cool if they joined Guybrush's crew. Granted, they did mutinied on Guybrush, but it wasn't because they didn't like him, but because they realized they wanted to be barbers more so then being pirates (at least that's how my train of thought works).
And I agree with LeChuck sitting out on the next game. He's a great villain, but it would be a fresh breath of air to see another menace for Guybrush to deal with.
I don't care, I said 40 hours. It's gonna be 40 hours. Player Be Damned!
-Ron Gilbert, MI2:SE Commentary