Instead of "Mihawk cannot be Zoro's Final Opponent because He isn't related to who i believe is Final Villain"
It's more Logical to say "Since Mihawk is created to be Zoro's Final Opponent, then that means He has a Boss who is Final Villain"
But then you will say "But Mihawk doesn't have a Boss, He doesn't take Orders from anyone"
Well, that's cuz Final Villain isn't revealed from the Start, only Teased & Hinted at
Who told you there isn't Someone who Mihawk looks up to?
One look at Mihawk's Design & you will realize that He has a Boss
You think He is Religious just for show?
Zoro is Eastern Swordsman, Mihawk is Western Swordsman
Zoro is Designed as a Samurai, Mihawk is Designed as a Knight
Zoro Bad with Directions, Mihawk is Clairvoyant/Sharp Eyes
Zoro is One-Eyed, Mihawk have Double-Layered Eyes
Zoro is Hard-Worker, Mihawk was probably born Talented
Zoro is Pirate Hunter, Mihawk is Marine Hunter
... etc
And finally, Zoro "I don't Pray to a God"
Isn't it obvious that Mihawk is his Opposite & does Pray to a God
Just like Kuma was holding a Bible & turned out to be a Priest indeed for Nika Church
Mihawk is similar but for a different Faith
Final Villain = Mihawk's Boss = Person He Worships
Existence of OPVerse God was questioned in East Blue Saga, Skypiea Saga, Thriller Bark, Fishmen Island, Wano ... etc
Just be Patient
Mihawk, Buggy & Crocodile are Zoro, Usopp & Nami of Final Villain
He isn't Introduced yet