I think that is the main message of this event as putting luffy's ability into OZ so that Oz will go againts Luffy's nakama since Luffy will surely not going to fight them seriously by any chance.

Oz will surely not going to hold back toward this fight since he was a demon in the first place....

It is a good opportunity to see whether Luffy's nakama can't bring him down or so...

It is also good to have perona in the crew, it may balance the gender count a bit, regarding her attiture, i think time will gradually change her ...