Zoro's opponent this arc will be Black Knight Sanji

>Multiple of the One Piece prototypes had a knight in the team, one was a rivalry between the samurai and knight which were a prototype of Zoro and Sanji
>Sanji fought against the Vinsmoke DNA corrupting him in Wano
>Sanji started saying he'd kill people more, such as calling himself the judge and executor in Egghead as well as he'd kill S-Shark, saying he'd kill the cat in Elbaf
>Little Garden is what kicked off the rivalry between Zoro and Sanji, the theme of it and the giants was the rivalry between crew mates
>Sanji had the knight helmet as a child
>called himself a knight and prince on multiple occasions
>his power up is skin armor and now flame armor, he was called black leg Sanji
>Sanji told Zoro to kill him if he ever turns evil
>he might even get a sword, it's been hinted at multiple times that he has insane blade skills and Zoro is mad that he won't use a blade
>we even saw him have a black raid suit akin to the god knights, which also acts as armor

Imu is going to exploit his lack of CoC and Genetic modifications that have evil traits to make him a God Knight and give us the knight vs samurai rivalry Oda planned from the beginning. The God knights already have flames, so he'll have black flame armor on top of his exoskeleton and already regeneration. It'll be a symbolic throwback to Little Garden.