Ah, I love One Piece RPs but they never seem to last long. ^^; Think the best idea would be to start with a small group as the main crew and build up from there.  Like, do occassional recruitment drives to introduce new crew members.  Just don't go overboard on the amount of PCs, basically. XD

And... Yeah, just have the players be part of one crew, like the Straw Hats, since having everyone all over the place... Really, something like One Piece could [i]maybe[/i] work as a sandbox if you put a lot of work into it, but it'd be a [i]lot[/i] easier to keep track of everyone if it's more tightly plotted.

Also, start off small in terms of power and work up, since it's more fun and rewarding to gradually gain power than to start off godlike.  Basically, no Logias, Mythic Zoans, etc.

[quote=@Archmage MC]
DO NOT be anal about powersets or characters. The less restrictive you are on stuff that aren't outright broken, the better things will be. Lots of RPs died after starting due to being too restrictive on character design.
[/quote]

Going to be honest: the one I [i]know[/i] you're thinking of doesn't make sense in One Piece. ^^;