Great post!
I want to adress something a lot of people keep bringing up about ZKK: Zoro undermining Luffy. There are a lot of ways for both character to get incredible moments without that happening.
For exemple, what if Oda doesn't retcon Zoan awakening?
Luffy could defeat Kaido in a 1v1 and break the " if it's one-on-one, Kaido will win" legend. Kaido would awaken some moments later, and be in some sort of primitive state (out of his mind, like the impel down guardians) and go on a rampage. At that point Luffy wouldn't be able to fight anymore. Zoro would be able to mortally wound a very powerful version of "Kaido" in dragon form (who could always regain consciousness for a brief moment at the end, and acknowledge him as a great samurai, but I don't think it's needed).
Luffy would defeat the "real" Kaido and get his Yonko moment, Zoro would kill a powerful dragon and get his legendary samurai moment.
I've only mentionned one way and it's missing a lot of important details (and obviously zoan awakening could be always be revised and used against Luffy), but I think that if Oda wants to make it happen, he will find a way to make both characters shine and not take anything from the MC, we don't need to think how. We can't ignore all the hints, ZKK or Zoro fighting Kaido again definitely has a chance to happen.