The plot could involve the First Cokage's reincarnation having some sort of mission. For instance, he might be reincarnated to stop an ancient evil that is about to be unleashed again. Since he has knowledge from his past life, he could use that to his advantage in battles and in making alliances with the current ninja clans.
In this fanfiction, the reincarnated First Cokage could also have an impact on the relationships between the different villages. He could try to bring about peace by sharing his old - fashioned wisdom of co - existence. He may start by trying to improve the relationship between Konoha and other major villages like Sand or Mist. He might also get involved in training the younger generation, passing on his unique skills and combat strategies.
The First Cokage's powers might seem less flashy compared to the modern ninjas. But he could still have an edge. His raw chakra control, which was probably more refined in his own era, could be a great advantage. For example, he could use simple yet powerful earth - style jutsus more effectively than some of the younger ninjas who rely more on flashy multi - element jutsus. Also, his ability to read the battlefield, which was honed in the battles of his time, could make him a formidable opponent even against the new generation of powerful ninjas.
One possible plot could be Hoke reincarnating as an unknown ninja in a small village. He then starts to show extraordinary abilities which draw the attention of the major ninja villages. Along the way, he befriends Naruto and the gang. He might teach them some new techniques that he remembers from his previous life. He could also get involved in the Akatsuki conflict, either trying to stop them in a different way or even trying to understand their motives from a different perspective.
One possible plot could be that a powerful villain tries to create a new Buu - like being using Naruto's chakra. But instead of creating a new Buu, Naruto is reincarnated as a hybrid of himself and Buu. This would lead to a lot of internal struggle for Naruto. He would have to deal with Buu's instincts while still trying to protect his village and friends. His friends might be initially scared of him, but over time they come to understand and accept this new Naruto.
The fanfiction could have a plot where Obito's reincarnation is not a normal one. He is reincarnated with a special mission from the afterlife. He has to find a way to bring peace to the shinobi world in a different way than Naruto did. He might have to face new enemies and also deal with the old grudges that still exist among the ninja clans. His reincarnation could also bring about a change in the relationship between the different villages as he tries to use his past experiences to create a more united and peaceful ninja world.
Maybe Naruto would have some of Ichigo's powers. For example, he could have a zanpakuto instead of a kunai.
In this fanfiction, perhaps Naruto is the reincarnation of Alucard due to some ancient prophecy. His journey would then be about discovering his connection to Alucard. He could start having strange dreams about Alucard's past life and battles. As he uncovers more, he realizes he has to use Alucard's powers to save the ninja world from a new, powerful threat that only his combined Naruto and Alucard abilities can defeat.
Perhaps the story could start with Naruto having strange dreams about Goku's life. As the story progresses, he gradually unlocks Goku's powers. He could then use these powers to protect the Hidden Leaf Village in a more powerful way. For instance, when the village is under attack by a powerful enemy, Naruto could transform into a Super Saiyan - like state, shocking his enemies and allies alike. His training would also change, as he'd have to learn to control his new Saiyan powers, which would be a whole new journey for him.
One possibility is that Naruto's reincarnation as Aizen would lead to a whole new set of battles. He might face off against some of the powerful Hollows or even the more powerful Soul Reapers who see him as a threat. His Naruto - based powers could be a huge advantage in combat. He could use his chakra control to enhance his sword skills or his ability to sense spiritual pressure. And his journey through the Bleach world as Aizen could be about finding a way to bring peace, just like he always aimed for in the Naruto world.
Well, the plot could involve Naruto being hunted by vampire hunters from a secret organization in the ninja world. These hunters don't understand that he's still Naruto at heart and just sees him as a dangerous vampire. Meanwhile, Naruto could be trying to find a way to use his new powers for good, like he always does. Maybe he discovers a way to use his vampiric abilities to enhance his jutsu.
Well, it could be that Naruto is reborn as a sort of hybrid of himself and Sephiroth. His appearance might change slightly, with some of Sephiroth's features. In the story, he might have to learn to control the new powers which are far more destructive than his normal chakra - based abilities. And his friends, like Sasuke and Sakura, would be both confused and worried about this new Naruto.