Ngl I think Kaido should've been a fishman.
Either a fishman x ancient giant hybrid, or a superannuated fishman breed like Megalodon or Dunkleosteous.
It would suit his "beast" motif, give a reason for his genetics, possible serve as BM's motivator for wanting a land where all were treated equal etc.
Also it would the whole fish turning into dragon concept.
His scales on on his arm even implied it too. I really wanted to see the Koido thing become reality, the memes were GODLY too but also Kaido being a fish who literally turned into a dragon would have been FUCKING BADASS and truly Yonko and WSC worthy.
Kaido the ultimate genetic chimera experiment, the Mewtwo or Cell of OP maybe.
I remember when the fighting bull fish appeared on Dressrosa, people linked them to Kaido lol.
I like how we still barely learned anything about Onis and Kaidos relation to Oars and such naturally. Also never learning the true name of Onigashima and seeing Pluton and the true Wano underneath current Wano that is also 3x bigger than current Wano. No surname for Kaido too. Kaido's favourite island being a winter island and futuristic/science themed (must be Queen related too naturally) never got explore and as I said earlier, no Kaido victory roar too.
Thanks Lolda lmao.