You obviously can only have one each of the unique pilots. But say you have the falcon with pilot Chewbabbaca. Can you then also use the Chewbacca crew upgrade card?

No you can not do that. Same thing with Luke skywalker. They are both unique characters which is covered by the rules saying that you can't field two ships with the same unique pilot on the one side (not even as pilot/co-pilot)

eventhough the force is strong with Luke he can only be one place at a time

That is what I thought also. I hadn't considered the Luke issue! The situation we looked at had Chewbacca pilot and Chewbacca crew upgrade, both on the Falcon. Withought looking it up in the rulebook, I thought unique had soem print about pilots. Where the second Chewy would have been an crew upgrade and not pilot. It makes sense that unique means only one, no matter what, but you never know sometimes!