the problem i have with the momotaro theory is if that happens oda effectively shits on all the buildup in act 1&2 for two characters introduced very late in act 3 to fight kaido.
Momotaro doesn't have to be anything more than a reference. Marco and Yamato don't have to be integral in Kaido falling. When I brought up Marco's dialogue for Chapter 999, it has nothing to do with Momotaro. I am plainly talking about his original intention.
The issue is, a lot of people can't get past the fact that whatever Act 1/2 plotline that was built for Zoro fighting Kaido is already over. We got an entire 10 chapter fight which had Zoro doing just that, as well as cutting Kaido. Nothing has been implied more was supposed to happen beyond it. In fact, Zoro himself already acknowledged to leave the fight to his captain. He has yet to utter Kaido's name in battle context since leaving the roof.
Whatever theory that is behind ZKK is totally separate from this. If that happens, it will happen way later after Luffy has won. It does not have to be related to what Zoro does when he recovers (i.e. fights King)