I'd prefer Bart to Ucy but he's got a crew to captain over, he'd be more suited as an ally like Law or Fishmen or Baratie etc., and I don't see Kinemon joining with Momo or leaving him, they'll stay together and I doubt they'll both join momo's just a kid.
I don't think anyone is gonna join at the first island into the New World but they may, but from everyone we've seen as candidates Ucy is the only one not restricted in some way. Bellamy has too much history with Doffy and will need time to figure things out on his own after learning Doffy o.k.'d his death, Bart has a crew, Rebecca/Viola/Kyros all have a kingdom to help re-establish, Cavendish hates Luffy, Sai has the Happo Navy to lead and be an ally with the SH's like Bart will, Don Quioxte pirates will probably be arrested it seems like Fujitora is turning in Doffy for the paper trick(unless I misread that scenario).
Ucy just seems like the most likely choice to accept. Luffy straight jacked a giant with a pissed off jet pistol covered with haki because he hurt Ucy. He hasn't really cared about any of the other newcomers except Bellamy and that's because they had a history.
