Then what is the purpose of killing (or beheading as it seems the scenario ZKK guys believe) an already defeated Kaido? That's not a big feat. That's just a murder and I wonder how would be Yamato's reaction seeing someone beheading his already defeated daddy (I think the relationship between Yamato and Kaido is not that bad. At worst it's similar to Judge and his son, and in end of WCI Sanji still chose to save his daddy who also gave him an exploding bracelet and gave him a beating).
Simple example scenario:
Luffy defeats Kaido and both of them pass out.
Kaido gets back up and Luffy doesn't.
A dragon goes towards Kaido.
Zoro protects Luffy from the dragon.
You're creating limitations on headcanon and possible paths Oda can take.
You can't ignore existing plotlines simply because you can't picture a way of it happening lol.
It's like people always suggesting the battle moving to the Flower Capital but the usual counter-response was "there is no way we can move to the Flower Capital". People always thought the
only way we could move to the Flower Capital was by getting defeated and etc... But Oda simply made Kaido pick up the island and now he's dropping it on the Flower Capital.
Predict outcomes, not paths to that outcome.