Since the voices in 4Kids version of One Piece seriously suck(well, Zoro and Jango's is an exception), who'd you want to play the OP characters. Ironically enough, all the VA's I'd want to play them are all from the Bang Zoom voice group.
Luffy-Joshua Seth(Taichi-Digimon Adventure)
Zoro-Lex Lang(Sanosuke-Rurouni Kenshin)
Nami-Michelle Ruff(Dojima-Witch Hunter Robin)
Usopp-Michael Reiz(Takuya-Digimon Frontier)
I'll post more characters later.