I don't really want Kuma to join. Not that he isn't an amazing character, but I kind of just want him to retire here on Elbaf with Bonney. He's already gone through way too much in his life, and him joining an Emperor's crew would just put even more stress on him as well as make it hard for him to raise Bonney which was what drove him to do most of the things he did in the first place.
I think that, if anyone else joins, it's just Yamato and Vivi.
I've come to believe that the Final War is going to encompass both the Realms of the Living and Dead; because of this, I'm more comfortable with Kuma dying than I was. I thought it would happen in Egghead, but, if Oda's trying to give Kuma's Fruit to Vivi like many have speculated, this makes more sense.
So, Kuma would die, meet Ginny in the "Spirit World", and we'd eventually see them again in the future during the Final War (I think we'll see Saturn then, too. I'm also wondering if Stella, when they return, will have been in "Hell", since their body has been dead for a while).
I'm hoping for Loki later (after messing around with Teach) Bonney, Tama, Yamato, Vivi, Karoo, and Carrot (I think Zunesha dies in Act 4). I'm also down for Momo sailing, but I'm not sure about it. Worst case scenario for me is Vivi getting kidnapped, I will throw something out a window.
I can also seeing Colon joining, especially if Gyaban dies.
Either 3 Apprentice Pirates (Newgate with Teach + Shanks and Buggy with Roger's totals combined), or 4.
Tama/Momo is a fun buddy pair, IMO.
I can see Colon being Bonney's Straw Hat buddy. Especially if both of their Dads die soon, like I sadly think they will. I think Kuma goes out here (Imu + Sommers + Garling potentially showing up scares me), and Gyaban and Rayleigh will die in the Pluton War.
Colon's gotten more screentime than I expected, and the excuse to have him paired with the group Gunko attacked was really weak; Oda clearly wanted to have Colon interact with the Crew, more.
Oda teasing Loki joining the Straw Hats, just to have Colon join instead, is also the kind of troll writing I've come to expect from this series. I think you can actually trace 90% of One Piece's current problems back to Pound surviving Whole Cake.