I get it. I also thinks it feels weird for Kaido to drop the Kanabo and go drink mojitos on some lost island beach somewhere. But the thing is...Kaido WANTS to die because it counts as a "win" to him. Die in glorious battle or whatever. So I also don't like the idea of having ZKK happen in a way that would legit satisfy Kaido.
Rewarding the dude who enslaved an entire country for decades looks dumb.
What would be the options? BB appears? Marines? To be fair, I would prefer the Marines to appear, Ryokugyu in specific for a simple reason: every admiral has their "moment". For Aokiji, it was when he appeared right before water7 and completely rekt Luffy Zoro and Sanji at the same time. Pure menace.
For Kizaru? Sabaody. Another show of pure power and threat. Akainu? Marineford. Fujitora? Dressrosa. Ryokugyu is the only one left to make a "big appearance". That's the only reason I would pick him over the other Admirals to show up now.
BB....I would rather for BB to be in WCI stealing the Road Poneglyph there.