As oscar put it, just make him into an NPC and have him appear when you feel it would be better for the story. Especially if we have a Skypeia arc.

Also, how will we all move this story along? I mean getting to the next part.

In short, are we all going to conveniently run into each other again in the next story and then the next? Or will we be split into groups (or in some peoples cases, by the crew they're in) and have different adventures elsewhere while occasionally meeting up with one of the PC groups later in the story? Like how Luffy occasionally bumped into Buggy (when he was chasing him and all) or Nami pre-joining the crew or whatever.

I just think if we all 'happen' to be involved in the same stories or whatever every time, despite being in different crews or whatever would just get rediculous. I know it'll be hard to pull off, but in One Piece you'd never see the Straw Hats always facing encountering the same people over and over.