1.) If he made a black blade it why couldn't he make another one?
You would have to prove that even if he made a lesser grade blade black, that it would somehow affect his swordsmanship to a degree where he's just nowhere near as strong, just because the blade was initially forged at a lesser quality
1.5) But we know black blades are the most elite and most durable, so it should have no problem containing Mihawk's haki and not shattering.
2.) If he didn't make it but attained it, and then tamed the strongest blade, you can say he earned the right to use it
2.5) . A sword canonically chooses it's user in this series, meaning if Yoru was already black it would already be the strongest blade that chose Mihawk, out of any other swordsman.
Therefore you would have to create a hypothetical in which Mihawk wasn't worthy enough to be chosen by Yoru.
You would therefore have to take away from Mihawk, the qualities that make him Mihawk, and he'd therefore cease to be the character "Mihawk", but a hypothetical lesser version
Once you do that, we're not even talking about Mihawk anymore. So it's pointless to create that scenario.
3.) Conclusion: He has a black blade because he's the "WSS Mihawk", meaning his capability of feats remain the same.
The only factor that might potentially limit his feats is the fault of the blade, not the swordsman, for not being able to handle the might of Mihawk's haki, he therefore in a hypothetical scenario where you gave him a dollar store blade, have to hold back on purpose
But since his swordsmanship is the greatest thing on the planet, he would have the best Haki utilisation in swordsmanship to adjust and make it work, so it might not even be an issue.