Someone's losing a lot of money not making one. I really think One Piece would handily translate into the SRPG realm, since everyone so readily falls into "classes," and like many SRPGs, the series relies on protagonists who are much stronger than the bulk of their enemies (except for a handful of boss-class enemies)

Imagine Fire Emblem: The Quest for One Piece, or One Piece Tactics. Bliss.

Like with Fire Emblem classes: Luffy as Lord, Zoro as Mercenary, Nami as Thief or Sage (clima tact and all), Usopp as Sniper, Chopper like the laguz, Robin as Assassin, Franky as General, and Brook as Myrmidon/Swordmaster. It all fits so well.

Anyone care to discuss this travesty of a missed opportunity?

One Piece is better suited to an Action-Adventure across the East Blue and the Grand Line.

Zoro should be a Myrmidon. Other than that, it would make a pretty good FE7 rom hack.