I wanted to see what people thought what qualities the next crew member should have, as opposed to discussing who it should be.
Personally the only position I can think of that hasn't been taken is Lookout, and Helmsman. But Zoro usually occupies the crows nest, and Franky is the one who usually controls every part of Sunny. There's Brigmaster too, but I don't think Sunny has a brig.
I always thought it was weird that the 3 strongest crewmates were in the original 5 from a weak part of the Blue seas. So i was hoping that the next crew member would be strong enough to be able to take on Luffy.