Well, it’d be a lot better than him coming back only as Luffy cheerleader #57 in the final war.
It’d make sense for Cross Guild and the Katakuri Pirates to ally with each other for several reasons. Cross Guild is a sham Yonko crew, with Mihawk and Croc being the only real muscle of the crew. They’re short on heavy hitters and also army size, so adding Katakuri, Cracker, Snack, Compote, Oven, Streusen, and the tens of thousands of fodders at their disposal would boost them to proper Yonko crew status. As for the Katakuri Pirates, Totland lost its protected status when their Yonko, BM, was defeated. Making Totland official Yonko territory again would be a good deterrent and help protect Katakuri’s family. Cross Guild needs to collect some RPs to stay in the race for One Piece, so it’d make sense for them to go for the one in WCI, which is the most widely known one. They can avoid a costly war to claim that RP by instead just allying with Katakuri. Allying with CG would also give Katakuri a means to try and get his sister Pudding back.