User blog comment:Videogamep/The Next Straw Hat Craze/@comment-1876594-20140227174959

In East Blue, the crew was made by "totally humans". In the Grand Line, they gathered an animal, a demon, a cyborg and a skeletron. If we add Jinbe, who is a fishman, the "collection" is complete. I mean: a member of a generic not-human race. It would be too boring if Luffy recruits a giant, a minkman, a dwarf, a longleg... too classic. "Fishman" represents the "not human" part of the OP world.

A Logia user would also complete the "collection", but there is the problem of the balance of the powers. To "solve" this problem I continue to think that Luffy would merge, in some way, the Mera Mera no Mi with his hat.