Which commander is there for him to fight tho?
King is a swordsman so there's Zoro to face him. If Zoro doesn't fight him because of the aerial problem, Marco (who is 2nd strongest after Luffy) will fight him.
Queen has a beef with Who's Who, Luffy, Kid and Killer. There is no build up at all for Sanji vs Queen.
Jack is set up for a rematch with the minks or to get his ass kicked by Luffy.
Smoothie isn't an option since Sanji doesn't hit women.
I'm not saying Sanji fighting a commander is impossible but given all the big hitters in the alliance, it's hard to predict who he'll be fighting.