After the scabbards are done fighting kaido, kaido will be decently injured.
Given that Zoro has ample foreshadowing to fight kaido and yamato fighting kaido is an absolute must as she is his daughter, I think that Kaido could honestly just be taken out by Zoro, Yamato, and Luffy, after the scabbards are done. I think that Luffy will have 2 rounds against kaido. One where he tag teams with Zoro and yamato, he will lose this round. then after he gets a heal by marco, he will have a 1v1 in a round 2 against kaido.
If this is the case, then it would allow Kid, Killer, Law, and Drake to take on big mom, likely with the help of others such as Sanji, jinbe, and brook(who's devil fruit counters the soru soru no mi).
Since Kid is a CoC user, the only other CoC user in the alliance apart from Luffy, and he does have the best portrayal out of any alliance member bar luffy, I think Kid will probably be the one who lands the finishing blow on big mom, as well as the one who gets most of the credit. But obviously it will be a tag team.
In any case, I think there are enough strong fighters in wano for big mom to be defeated without the use of any plot.