Anyways I think big mom should be taken down via a team effort. Luffy will get help against kaido of course, but Luffy's already a low top tier, so I think that Luffy can and will do most of the work against kaido himself. despite the help he gets, Kaido's defeat will properly be credited to Luffy.
But I feel like big mom will be a true tag team with no one character getting a majority of the credit. In addition to Eustass Kidd, Law, and Drake, who I'm sure will help out, I think there are a bunch of people who could join the fight and help take BM out.
the whitebeard pirates are surely coming to wano, given their connection to Oden. Given shanks's connection to Oden, I feel as if we might see one or two red hair commanders arriving as well. And lastly, you do have the blackbeard pirates, who would probably like to profit off the wano situation in some way.
I can see:
Kidd, Law, Drake, Marco, Jozu, Vista, Beckman, Lucky Roo, and Shiryu vs Big Mom