I know this is because of C4N but why does this have to be relitagated for years and years, yes Carrot, Yamato and Vivi can all easilly become nakama if Oda wants them too, are they right now? No
You just need to write Carrot running away from being king of Zou to the SH and them going "sure whatever join", Yamato to just have Momo be strong or have some mini time skip going to the SH and them going "sure whatever join" or Vivi comming to them and asking for shelter and the Sh going " yes vivi-chwan sure".
They all have weak and strong points but at this stage, anything goes to be honest. If anyone is saying its too late to introduce new nakamas at say Elbaf, this better be the last arc where someone gushes for a new nakama of the week.