User blog comment:Fintin/How Many More?/@comment-1876594-20100628214638

Luffy doesn't need any specific worker, but Robin and even Zoro (a warrior with no utility in travelling) show that there could be some addictional "useless" member. The only condition is that they can fight. I'm thinking about an indovine: a funny character, weak as Usopp or Nami.