One possible plot twist could be that Naruto not only saves them physically but also manages to change their view on the world so much that they become allies with Konoha. For example, Naruto might show them the true meaning of friendship and loyalty, which makes them question their previous life of being mercenaries. This could lead to a whole new dynamic in the story where they use their skills for good instead of just for money or power.
Maybe the way Naruto saves them is by sacrificing one of his own powers. Let's say he gives up some of his chakra to heal Haku and Zabuza when they are on the verge of death. This act of selflessness could earn their respect and loyalty. They might then vow to protect Naruto and Konoha in return, creating a very interesting bond between them. It would also change Naruto's own journey as he now has to adapt to having less chakra.
A plot twist could be that when Naruto saves Haku and Zabuza, they find out that there is a greater threat looming over the ninja world that they all need to face together. So instead of going their separate ways, they form an unlikely team. Haku and Zabuza bring their unique skills and knowledge of the criminal underworld, and Naruto brings his determination and the power of the Nine - Tails. This new team has to overcome their differences and work together to stop this new threat.
One possible plot twist could be that Naruto's near - death experience unlocks a hidden power within him. Maybe a new form of chakra that he didn't know he had. This power could be related to his Uzumaki heritage. Another twist could be that Haku, instead of being just a damsel in distress, has some secret knowledge or ability that she reveals after Naruto's sacrifice. For example, she might know a special healing technique that she uses to save Naruto at the last moment. And finally, there could be a political plot twist where Naruto's near - death is used by certain factions in the ninja world to their advantage, creating more conflict for the Leaf Village.
One possible plot twist could be that Naruto develops a much darker and more ruthless side due to Zabuza's influence. Instead of the optimistic and friendly Naruto we know, he might be more solitary and calculating in his approach to battles and relationships. For example, he could be more willing to use underhanded tactics like Zabuza's use of hidden mist jutsu to ambush opponents.
One possible plot twist could be that due to Zabuza's influence, the female Naruto becomes more of an assassin - type. She might develop a different set of values compared to the original Naruto. For example, she could be more ruthless in combat and less hesitant to take lives when necessary.
A plot twist could be that Zabuza's past and his relationship with Haku are revealed to Naruto in a different way. This could lead to Naruto having a unique understanding of loyalty and sacrifice. He might then develop his own version of the 'ninja way' that combines the values of the Leaf Village with Zabuza's more self - serving but also protective nature.
One possible plot twist could be that Zabuza has a change of heart and decides to train Naruto secretly on their journey. He could see Naruto's potential and want to make him a stronger ninja, which would completely change Naruto's fighting style later on.
A really interesting plot twist could be that Zabuza has a hidden past or connection to Naruto's family. For instance, perhaps he knew Naruto's father in a different context than what was previously known. This could change Naruto's whole perspective on his family and his place in the ninja world. Or, Zabuza could have been given a secret mission long ago related to Naruto that he never fully completed, and now raising Naruto becomes a way to fulfill that mission. This would add a whole new layer of mystery and depth to the fanfic.
One possible plot could be that Sakura, being a skilled medic in the Naruto universe, comes across Zabuza and Haku who are severely injured. She decides to use her medical jutsu to save them. Maybe she's on a solo mission and her sense of morality makes her help them, despite them being former enemies. This could then lead to an interesting alliance or at least a mutual respect between them.
One possible plotline could be that Naruto arrives just in time to stop Haku from sacrificing himself for Zabuza. He uses his shadow clone jutsu to create a distraction and then manages to pull Haku out of harm's way. Naruto then tries to convince Haku that there is more to life than being a tool for Zabuza.
One possible plot twist could be that Zabuza's training methods lead Naruto to develop a darker side. Naruto might start to question his own values as Zabuza's more ruthless ways of fighting seep into his mindset. For example, he could become more willing to use underhanded tactics in battles, which would shock his friends.
One possibility is that Naruto could learn new combat techniques from Zabuza and Haku. Zabuza is a very skilled swordsman, and Haku has his unique ice-based jutsu. Naruto might pick up on some of their skills and incorporate them into his own fighting style, making him even more formidable in future battles.