Some of my readings also suggest that if there's going to be any occasional or one-off contributors, you might want to settle early all of the important "money" issues and questions.

GPL and CC do prevent quite a few problems in this regard, but won't do anything for people getting surprised or feeling wronged for some reason or another. The usual recommendation is to keep written records and archived copies of everything, including discussions and threads like this one.

I'd agree that for simplicity, just go GPL for the whole thing. I can't see why the license and rights owner couldn't change the entire licensing model at a later date anyway, but I'm no expert. This could also be one of the things people could be uncomfortable with as the project nears completion, though.