I actually think Oden would set sail with Luffy, actually, and trust Momo / the new Shogun and the 9RS to rebuild Wano. Oden / Roger lamented not being able to meet Joyboy and change the world. Also, Yamato seems privy to some things that probably only ex-Roger pirates are. He all but demanded to set sail with Luffy in his intro. Not to mention Luffy freed him from the bondage Kaido had him in. I think there's a duality in him and Momo. Momo is likely Uranus (ability to command ancient animals), and will "build up Wano", whereas Yamato is the Oden-like counterpart who desires adventure above all. Momo has already had adventures - being trapped in Punk Hazard, being on Dressrosa, Zou, Wano, nearly executed, etc.
I don't think roles matter too much at this point. Jinbei is a helmsman but that didn't become necessary until it was necessary (surfin' the Big Mom candy tsunami). They would find something for Yamato. In general having a pretty strong female fighter is a breath of fresh air.
I think in a nutshell Yamato's desire to be present when Joyboy changes the world and ushers in some new era will overtake any desire to stay on Wano.
So my vote: New Nakama. Too many emotional moments not to be. Yamato was practically researching and waiting on Luffy to make his way to Wano.