I actually was thinking about this same topic today. Since Nami is with Sunny, how can they navigate to the next location. I was thinking maybe Kinemon might have some navigation skills, or some of his men they are trying to rescue, but having the revolutionaries there and going with them makes more sense.
I was also thinking of the possibility of splitting the storyline in two and having the reader follow two separate stories until their paths cross again. It would be really different and a break from how the traditional format of the SH's landing on a new island goes.