I'm guessing that the crew would defeat Oz, but be left barely standing. Then Luffy finally finds his way and beats the crap outta Moria. Or something along those lines. Now that seems more One Piece-ish to me.
Hmm.. Kuso IX Kuso, I'm guessing that will be less likely to happen. The thing with Cindry worked because she was a majorly kind-hearted soul in the first place, and the will that stayed in her body after her death sort of "took over" the shadow placed in her. But Oz, on the other hand, was some legendary demon criminal lord from some frozen island. I don't think appeal to emotions would work well against him. Even so, Luffy's will is probably too powerful to be talked into, and that will is under Moria's control. In other words, my opinion is that they'd probably have to tank it out with Oz.
But that's just my opinion; you don't have to agree.
I wonder what happened between Shanks and Whitebeard too. I can't imagine either of them dying, so I think they probably stopped to talk it out or something.