Would the Hyuuga even allow him to keep the eye? I mean, these are the people who gladly enslave their own kin and force brothers to sacrifice each other just to keep their bloodline in the family. I still have no idea how Kakashi was allowed to keep his Sharingan. You'd think the Uchiha would be nagging the Hokage to death over that crap. At the very least I doubt Byakugan Kakashi uses Jyuuken if only because the Hyuuga would go APE$#!+ if he did. In any event, the first fight with Zabuza would be harder. He'd be able to see through the mist, sure, and even have a better chance of avoidng getting caught, but without Sharingan hypnosis he's not beating Zabuza right away. He'll win, but he'll be roughly as drained as he was in canon. Also, he can't kill Azabuza, even though he knows Zabuza is still alive, because then he'd have to fight Haku and doing so while exhausted is suicide. Second fight is anyone's guess. Zabuza isn't stupid. He wouldn't rely on the mist knowing its worthless so he'll have some different strategy in mind. Depends entirely on what he Zabuza's new plan is really. He does fine during the Invasion (if he survives Zabuza's second fight). Nothing noteworthy. Itachi still stomps him and makes hundreds of Hyuugatards rage in the process. No Kamui means Deidara wrecks his $#!+ though. He eventually gets blown up, Naruto goes nuts and no one can stop him, and Deidara runs away until Naruto burns himself out then collects the kid. Rescue Gaara Arc ends in disaster (after collecting the unconcious Naruto Deidara returns to the cave, finishes off the weakened Sakura and Chiyo, and hands Naruto off to Zetsu and Tobi/Madara. Rescue Naruto Arc is just Leaf and Sand blindly searching around because they have no clue where Naruto is and Naruto losing Kyuubi. Even if he survives the extraction the Akatsuki would notice and kill him. Manga ends eventually with Madara ruling over the world thanks to his Mugen Tsukiyomi.