Good point mate. Zoro and Sanji have different narrative functions, they're not equals.
About CoC, Sanji doesn't showed the "qualities of a King". Also, i don't know how work these cover hints, but i think isn't impossible for him awakening that, specially after Don Chinjao.
Oda need to explain better how Haoshoku works, if it's something you born with, or you can get through a great determination and willpower; If it's the second option, seems like Sanjino can get this cause his lack of determination and confidence in some moments are one of the main themes of his character, so if oda decide to give him CoC, he would use that development's line.
For now, i don't see this happening.
About CoC, Sanji doesn't showed the "qualities of a King". Also, i don't know how work these cover hints, but i think isn't impossible for him awakening that, specially after Don Chinjao.
Oda need to explain better how Haoshoku works, if it's something you born with, or you can get through a great determination and willpower; If it's the second option, seems like Sanjino can get this cause his lack of determination and confidence in some moments are one of the main themes of his character, so if oda decide to give him CoC, he would use that development's line.
For now, i don't see this happening.
I think you are born with it and you awaken it