Assuming Kozuki Moria joins Cross Guild, he likely not only knows about reading poneglyphs, which would give Cross Guild an advantage in this battle royale for One Piece, but Pluton as well. Crocodile is also interested in Pluton, so that's plenty of motivation for Cross Guild to sail to Wano.
Caribou is also about to tell Blackbeard about Pluton, something he'll likely be interested in given how he always wants to gain power. So after he takes Pluton, Cross Guild can then show up to be proclaimed as the heroes who will get Pluton back from Blackbeard, with Yamato's backing since Yamato would feel responsible for not being able to safeguard Pluton. The situation with Momo can easily be resolved with Oda powering Momo up like he did with Tama, enough to convince Yamato to finally leave, which would eventually lead her back to Luffy while she tries to get Pluton back.
Caribou is also about to tell Blackbeard about Pluton, something he'll likely be interested in given how he always wants to gain power. So after he takes Pluton, Cross Guild can then show up to be proclaimed as the heroes who will get Pluton back from Blackbeard, with Yamato's backing since Yamato would feel responsible for not being able to safeguard Pluton. The situation with Momo can easily be resolved with Oda powering Momo up like he did with Tama, enough to convince Yamato to finally leave, which would eventually lead her back to Luffy while she tries to get Pluton back.