I dunno, maybe it's just my strange idea of "First Mate", but apart from the fact that the Straw Hats don't really have a traditional chain of command, Zoro is doing the job of supporting his captain better than any other crewmember. I view him as the First Mate by that virtue alone, due to the aforementioned lack of a chain of command.
The fact that the others have their own duties to attend to also helps. (Gunner, Cook, Navigator, Doctor, Archaeologist, Engineer, Musician)
|