The Answer is never "Quantity",
When Zoro faced Hatchan who had more Swords, He proved to him that Quality > Quantity,
Also when Zoro fought Daz who can make a thousand Cuts, He proved to him again that Quality > Quantity,
Same for his other Opponents,
So i don't think Zoro is gonna become WSS by saying "Oh look, i beat Mihawk cuz i had more Black Blades than him",
Same goes for Unlimited Ashura or anything where it's about Maximizing Quantity rather than Quality,
Black blades imo aren't the solution to Fight Mihawk, They are the Requirement to be able to challenge him again,
We already seen Mihawk mention it to Zoro during their Training, implying that Mihawk expects nothing less of his Student,
And it's not like Zoro didn't own a Black Blade before,
So He should do this Feat against his Next Major Opponent, before facing Mihawk.