Would you like it if shiryu killed mihawk and became WSS?
Shiryu vs Zoro is much better imo since Mihawk is zoros teacher and Shiryu carries a katana just like zoro
Shiryu is another Mr. 1/Kaku/King, no where does he have the same buildup as Mihawk with regards to Zoro's character. Oda is definitely not gonna have another character invalidate the 20 year promise between Zoro and Mihawk.
Zoro vs Mihawk round 1 was a proper 1v1 duel where Zoro placed his life on the line to fight for his dream. And Luffy spectated.
Zoro's endgame fight for the WSS title will not be a fight where he fights the #2 of the opposition as the #2 of the Strawhats, in service to Luffy. It will be another 1v1 duel with the entire Strawhats or maybe even the entire world spectating, as Zoro places his life on the line fighting for his dream. Only this time, Zoro would win and his name would reach the heavens.
Even after beating King, look at what Oda made Zoro think about, "
From now on to the day I beat him to become the Greatest Swordsman...".
Shiryu or no other opposition #2 would take the title away from Mihawk, it is solely Zoro's job to do so.