I think you sell Usopp short. What Usopp lacks in brute strength he makes up for in brains and guts. Yes I said guts, he's the bravest one in the room when the midden really hits the windmill. I still say he takes on Kaku. And I still say Baskerville VS Somebody, maybe not luffy because luffy's declarative statements almost always come true, and he did say he would fight Lucci.
I also think baskerville will fight because there are nine straw hats (counting Franky and Robin) and eight CP9 members
EDIT: Oh, and the fight with luffy? He messed luffy UP. Go back and look at that, Luffy was bleeding all over. Yes he beat Usopp with one punch, but look how much damage got done before that punch was landed. AND usopp pulled that reversal with the dial on Luffy's ass. He countered two of Luffy's mainstay gum-gum moves–bazooka and gattling gun--and whipped out some sneaky tricks (his use of gundpoweder star)
I'm not saying Usopp's on Luffy's level, I'm saying give credit where credit is do.
And Alex, if that's you I'm hunting you down with a pitchfork at school tomorrow.