Wow. Back to your Zoro doesn't have ACoC.
Where is the swordmaster code that says the WSS can't fight a swordsman with 1 arm. The fact Mihawk is waiting for a swordsman stronger than 1 arm Shanks tells us him having a 1 arm is irrelevant and not a problem. Mihawk called Shanks an one arm has been. Key word "has been", a person or thing considered to be outmoded or no longer of any significance.
The manga tells us Mihawk has greater swordsmanship skills and is the WSS. The WSS part is the manga way of saying Mihawk is stronger.
It's really not that hard.