Well the way these things go usually is we have at least 1 pirate crew and sometimes some marine fellows running around as well. Finding One piece and the benefit of crews is generally a good reason to get into a group of some sort. One of the problems I foresee is a lot of weight is put onto the GM to put a plot out for each island people go to. Perhaps if we had everybody 'make' an island adventure and co-gm/gm it when a group gets there to help spread the weight around so to speak.