Honestly think you're on to something here. But you've got it the wrong way round imo.
Zoro initially wanted to become the Greatest Swordsman so his name could be heard in heaven where Kuina could hear it. However over the course of the story, but particularly with recent developments, Zoro is now "the king of hell" and uses cursed blades, etc.
In One Piece, demons/devils have always been portrayed as the good guys - people who want freedom and not to be under the heel of the "Gods" of the Celestial Dragons or Imu - who are portrayed as the bad guys.
And over the course of the story but particularly in Wano the Straw hats have became more demon-like. There's Robin with her deal, Sanji's "Diable Jambe" meaning devil dance or something like that, Brook an undead soul king, and Luffy, the reincarnation/representation of Joyboy, who has a lot of snake imagery (Joyboy not Luffy), which I can't be bothered to get into now.
Zoro, who originally wanted to get his name into heaven, lost to Mihawk, a man who looks like a Spanish conquistador, who has a giant cross for a sword and a literal cross on his chest - very Christian themed. So Zoro, not wanting to lose again, changed his tune and became demonic, like the rest of the crew. It makes sense that Zoro, the now "king of hell", will finally fight and beat Mihawk for the title of Greatest Swordsman, proving the way of the demon to triumph over the Gods. Which ties in to how the Straw hats will eventually take down the Celestial Dragons and the WG.