Just to register it here.
I think the "Queen - Judge" thing is gonna have a part to play, but not as a justification for Sanji fighting Queen.
I think Judge extracted King's bloodline elements just like Vegapunk extracted Kaido's. Vegapunk created the replicated DF, while Judge applied it to the modifications on his children. Queen might have been part of the team that studied them, and that's howhe met Kaido and later joined him.
King being the "Wildfire" IS NOT something just for show.
Maybe his race is like the Genasi from DnD. A race touched by the Elemental Planes, that can use some elemental powers to an extent. That would be dope AF.
Another possibility is that Judge used King as a subject to test his enhancing project and gave him the fire power. His race has nothing to do with it. But it was a failure and King has an entire burned body, like Dabi, so that's why his entire body is covered, even his face.
King's clothes are a Raid Suit prototype made to protect him from burning himself to ashes.