We don't have enough information about Rebecca, but she is more likely to be a temporary crew member.

Quote Originally Posted by Hart_lerouxx View Post
^another crew member? Yes!! We're dying after Jinbe postponed.

I still believe Sanji would eat d mera2, or maybe he enter d tournament to kill violet's target.

Btw, just wonder. Kaidou most likely send his elite crews to dressrosa. Where re they? Could it be, 2 elite crew from 2 Yonkous, and 1 top pirate+escaped prisoner from lv 6?
Still, luffy is way too strong for em.
I don't think Jimbie ever meant he would travel with the crew, but when Luffy said he'd put Fishman Island under his protection he would join Luffy as a ally (like he was with White Beard).
Also, I doubt Luffy can 1v1 a lvl 6 prisoner easily, if at all (of course I'm sure there are some he could beat, just as a rule of thumb I don't think he could easily beat one)