I still think that Carrot gonna join the Strawhats crew, she has lot of potencial and with some training in haki she would be very powerfull.
Also the fit to the crew, she came alongside with the strawhats to Whole Cake island, her friend die(like the strawhats having someone who die in their past), she was a really good part and add something to the strawhats, I hope Carrot joining them.
jimbe from impel down to wano got so many arcs before he joined and he still didn't join yet lol, and story already at 80% so it makes no sense for anyone to still join part of the main cast. carrot fans pushed her but she got lost and faded into background since wano started lol, and BB having 10 captains could just be because luffy will beat one of them before his proper battle with BB himself, like he beat both katakuri nad cracker besides BM, like burgess or something.
Maybe one more? It depends if Teach is considered one of the Ten Titanic Captains or not. the SH main crew and BB crew is going to match at Laugh Tale, each fighting their opposites based on crew-roles (Zoro vs Shiryuu, Burgess and Jinbe, etc). IIRC, Jinbe makes ten SH's with Luffy, right? So if BB has one more, then we'll need someone like Carrot to join up.