Now that WCI arc is coming to an end and Caesar appears to be free I think he might get involved with or even join the Blackbeard Pirates. Perhaps he'll be the "Buggy" of BB's crew.
A long forgotten question from Punk Hazard was why Aokiji traveled there in the first place. Very few people knew of what was going on at Punk Hazard as the island was believed to have been made uninhabitable as a result of 1) the poison gas incident 4 years prior and 2) Aokiji and Akainu's duel which turned the place into half frozen wasteland, half volcanic hellfire. Even more-so was that Monet and Vergo's missions were so top secret that, if I recall correctly, only Doflamingo and maybe his top officers knew of there whereabouts.
Doflamingo's home-base was Dressrosa and Doffy had only just arrived at Punk Hazard before Aokiji showed up. If his goal was to take Doflamingo out he could have easily done so.
By process of elimination that really only leaves one reason why Aokiji traveled to Punk Hazard – for Caesar. Smoker himself questioned Aokiji and stated that only people involved in Underworld dealings would have known about the location and activities on PH.
I don't know why Aokiji wanted Caesar, especially given his questionable loyalty towards BB pirates. That we'll just have to wait and see.
Another tidbit, in the One Piece Green databook it contains early concept art of the BB's crew. Obviously some of those people changed over time. Kitsune probably became Catarina Devon. Last Lion might have become Avalo Pizarro. Basurero Shot is now Vasco Shot. Lapaix Jesus is now Jesus Burgess.
However, there's another crewmate that appears to have been erased however his name or title was "King Joker"
Perhaps
King –-> Caesar
Joker ---> Clown
Now that Caesar appears to be free of both Big Mom and Kaido, assuming Shanks isn't involved heavily in the most nefarious underworld trades, that really leaves BB (and I suppose WG) as the biggest customers.
Unrelated, the real life Blackbeard had the pirate "Black Caesar" serve as a lieutenant aboard the Queen Anne's Revenge.