The thing is non advanced CoC doesn't really make you any stronger, while on advanced stage it's probably super powerful or helpful, either one of them or both.
So if Zoro gets CoC it's not really worth much in actual combat, but it would just be super cool for his portrayal and it certainly fits him a lot. He definitely has the qualities of a king. And even before Rayleigh, people have seen this coming since a long time.
Arlong hyping him up, Mihawk respecting him for his determination, his vice captain role during the Ussop scene, that Thriller bark accident.. Just to name a few.
And now we even see him beating up uprising stars that lack exactly that quality, basically showing them their place.
I'm really curious to know if all the top tiers will have CoC just by default or if Oda has some kind of cop outs like extremely powerful devil fruits taking over that job, where their fruits are that what's elevating them to that level even though they lack the qualities of a king (Blackbeard and some admirals perhaps)