In hindsight, maybe the best way for Zoro's dream to become World's Greatest Swordsman would be if it wasn't just Mihawk alone he had to beat. Like, there were a grouping of sorts of the world's finest and beating all of them would make Zoro the GS.
Like, let's say Mihawk, someone from each crew of the Yonkou and a Marine. And Aramaki, even before he became an Admiral?