Vortex yes I suppose in a way they all have to be pirates, but not of the plundering type. Everyone signs a "contract" to the ship. Cooks, tailors, (to sew up a torn sail and fix clothing) doctors, many many skills can be used on the ship. So I guess that's a yes and a no. Haha. Eventually, though, they're going to be on an island as I said in the plot, so other characters from there can be added later.