Jinbe was a captain of his own, for a very long time, and the scene at WCI with his crew should be a testament of his good leadership, he is experienced and knows how to remain calm, he would be a very good asset to the strawhat crew i believe, if only he wouldnt be dead already
Brook was also a captain of his own, though im not sure he now is serious enough to be even considered as an option...
Franky got the aniki stuff going for him, and seeing him being straight forward with luffy about not giving a fuck about his decision and that he would help the tontatta no matter what could be aspiring to some, i guess.
I dont have anything to add on the usual suspects like zoro or luffy.
