I know yall dont believe in the set-ups for Sanji vs King, so let's go by process of elimination.
Marco vs King: Cannot happen - Marco isnt New Gen. It isnt his role
Zoro vs King: Cannot happen - Zoro isnt interested in King, he only wants Kaido. Oda wasted any oppturnity he had to set this fight up.
Jinbe vs King: Cannot happen - No set up and already has an opponent
Now we have two options for King: Yamato or Sanji. Tbh I'd rather see people spouting Yamato vs King then Marco vs King. So go at it lmao.
But logically...just go for the fight Oda is setting up too.