If Oda didn't want Carrot and Yamato on the crew, he could have had them invited to the grand fleet, that hes completely forgotten in his senility.
Oh wait I forgot, Shanks instead of reuniting with Luffy, came here to bully an Admiral with his crew and having the authors favour/plot armour, bait us immensely with Luffy and thus Yasopp and Usopp too, promote his movie, then fuck off to bully an even much weaker and thus easier target than Aramaki in Bartolomeo for no believable, good reason.
But yes, we could have had Carrot lead the Minks in a Zou based division of the GF and Kinemon/Yamato/Momo bringing up the Wano equivalent with samurai, Ninjas, tamed gifters and whatever.
But nah because LOLDA.
Luffy took on Yonkos twice now with FAR bigger crews and armies than his and he didn't even have his fleet, even vs a double Yonko alliance!
Who needs a Grand Fleet when a little girl can brainwash and enslave one Yonkos army of fodder freely and one of that Yonkos commanders as well as the other Yonko does more damage to their own side/military force than the enemies ultimately.
The Grand Fleet would have drastically made up the numbers vs the Yonkos and at least Barto and Cavendish were considered newer Supernovas I believe too? They're definitely strong and capable.
.
Remember Elizabellos Yonko beating punch? Or that Barros barrier blocked that punch easily and also an enraged Oden too?
Fuck this arc, man.