One interesting plot twist could be that Ichigo's zanpakuto spirit interacts in a unique way with Naruto's chakra. Maybe it gives Naruto the ability to use some Hollow - like powers, which would completely change the dynamic of his battles. Another could be that Ichigo's past memories start to surface in Naruto's mind, leading to confusion and also new insights into combat and relationships. A third one might be that the concept of the Soul Society in the Bleach world somehow merges with the ninja world in Naruto, creating a whole new set of rules and power hierarchies.
A really fascinating plot twist could be that the Hollowfication process that Ichigo experiences in Bleach is reincarnated in Naruto in a new way. Instead of becoming a Hollow, Naruto starts to develop a dark side that is related to the Hollow energy but is manifested as a sort of shadow - clone - like entity. This entity has its own will and wants to take over Naruto. Another plot twist is that the Soul Reapers' duties in the Bleach world are translated into the Naruto world as Naruto having to protect the spirits of the dead ninjas from some sort of evil force. And the last one could be that Ichigo's relationship with Rukia is reincarnated in Naruto as a relationship with a female ninja, but with all the complex emotions and bonds that Ichigo and Rukia had.
Well, in some fanfictions, a cool plot twist is when Ichigo's Quincy powers are reincarnated into Naruto in a way that Naruto has to learn to control this new form of energy. It's different from chakra and it causes all sorts of chaos in the ninja villages as they don't understand it. Also, the idea of Naruto having Ichigo's bankai but in a completely different form due to the different nature of the Naruto world. For example, instead of a sword - based bankai, it could be a giant beast made of spiritual energy that Naruto can summon. And then there's the plot twist where Ichigo's friends from the Bleach world are reincarnated as some of Naruto's comrades, bringing their own unique skills and personalities into the mix.
Perhaps a major plot twist is that Naruto, as the reincarnation of Izuna, has a special ability related to the Uchiha's Sharingan. Instead of just having the Nine - Tails' power, he now has some sort of unique Sharingan - related power that no one has seen before. This could lead to new alliances and rivalries. Also, it could be that Izuna's past relationships start to resurface through Naruto. What if he has some sort of pre - existing connection with an old Uchiha enemy that now becomes a problem for Naruto and his friends?
One interesting plot twist could be that Naruto's friends initially think he's been possessed by an evil force and try to stop him, but later find out that he's actually the key to saving the world from a greater, hidden threat related to Sauron's power. Another twist could be that the Akatsuki are somehow connected to Sauron's minions from Middle - earth, and Naruto has to team up with some unlikely allies to defeat them.
One interesting plot twist could be that Naruto starts to have memories of Tobirama's past battles. This would make him question his own identity and purpose. Another could be that Tobirama's reincarnation in Naruto causes a shift in the power dynamics among the villages. It might make other villages see Konoha as a greater threat or as a source of new knowledge.
One popular plot twist could be that the reincarnation of the god gives Naruto powers that are completely unexpected. For example, he might gain the ability to control time, which is a power not seen in the original series. This would change the whole dynamic of his battles and relationships.
Well, a great plot twist could be that the enemies of the village learn about Naruto being Minato's reincarnation and try to use it against him. They might try to manipulate his new - found connection to Minato in some way, like using it to create doubts in Naruto's mind about his own identity. Another could be that as Naruto is the reincarnation, he has access to some of Minato's special chakra that has unique properties. This chakra could react in unexpected ways when combined with Naruto's own, leading to new powers and abilities that no one anticipated.
Another interesting plot twist might be that Indra's reincarnation has memories of all his past lives from the very beginning. This would give the character an unprecedented advantage. They could use the knowledge of ancient jutsu and strategies that were long forgotten. It could also lead to a moral dilemma as the character has to decide whether to follow the same path as Indra did in the past or break free from the cycle of hatred.
In some fanfics, a great plot twist is when Ichigo's Hollow powers are misinterpreted by the DxD characters as some sort of devilish power. This leads to a lot of misunderstandings and conflict at first. Another interesting plot twist can be when Ichigo somehow ends up being related to an important figure in the DxD world through some convoluted backstory.
Maybe Naruto would have some of Ichigo's powers. For example, he could have a zanpakuto instead of a kunai.
Another great plot twist could be related to the memories of the reincarnation. Instead of gradually remembering past lives like in typical reincarnation stories, the reincarnation of Rikudo Sennin has all the memories at once but can't control them. This could lead to some really chaotic and interesting situations where the character is constantly fighting between their current self and the memories of a powerful sage.
In 'Twisted Fates', the plot twist is that the powers of Ichigo and a certain devil in High School DxD get merged accidentally. This leads to a new form of power that no one expected. It causes a huge shift in the power balance and makes both the allies and enemies of the characters scramble to adjust to this new situation. This fanfiction then delves into how they all cope with this unexpected development.