Re: the Search for Strawhat's New Nakama...
Who said the shaw hat got or the officer seat cover? I think there still several seat open
1. Musican like everyone said. Merman always famous for their voice. Therefore, I think a female merman should do the job.
2. Messenger, who do the information control (Like RockStar in Red Hair crew)
3. Business man to deal and buy stuff with people (I think Nami do just fine, but her main job still is Navigation, business is not her main job - just like Ussop can repair ship but he is not a shipwright.)
If we count all three of this of these in to SH crew, it will be exactly 10 members like Luffy always wanted.
Addition that also likely possible.
4. Scientist, who invent machine, and provide a way to increase power for DF user.
5. Blacksmith, who make weapon for SH crew (Ussop can do this, but like i said earlier, he is not a professional for this job, just like he can fix the ship but not a shipwright. Ussop has limit skill for this job, like when he make the tastic for Nami, he didn't know the real ability of the tastic himself)