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.
Well, the plot could involve Naruto being a huge fan of Goku through some kind of inter - dimensional viewing device. He starts to mimic Goku's training regime, much to the confusion of his friends in Konoha. Then, an evil force from the Dragon Ball universe somehow crosses over to Naruto's world. Naruto, with his new - found inspiration from Goku, decides to take on this threat, and in the process, he might even convince Goku to come and help him save his world. Along the way, there could be lots of comical moments as Naruto tries to explain ninja concepts to Goku and vice - versa.
In fanfiction, the concept of Naruto being Goku's reincarnation is not unheard of. Fanfiction writers like to blend different fictional worlds to create unique stories. If Naruto is Goku's reincarnation, it could mean that he has a different kind of chakra, perhaps more related to Ki energy from Dragon Ball. This could also affect his relationships with other characters. For instance, Sasuke might view Naruto's newfound powers with suspicion or envy, and Naruto himself might struggle to come to terms with his new identity that has roots in a completely different anime world.
Well, one possibility is that Goku, with his powerful Saiyan abilities and big heart, teaches Naruto new combat techniques. Maybe he shows Naruto how to better control his chakra by using some of the principles of Ki control in the Saiyan way. For example, Goku could help Naruto reach new levels of power in his Rasengan by adding elements of his Kamehameha's energy concentration.
In a 'Goku adopts Naruto' fanfiction, perhaps Goku accidentally travels to the Naruto universe. He comes across Naruto, who is an outcast in his village at that time. Goku, not understanding the social structure but seeing Naruto's potential and loneliness, decides to adopt him. Goku teaches Naruto about the concept of Super Saiyan and how to harness his inner power in a different way. Naruto, in turn, shows Goku the beauty of ninja techniques. They might end up fighting against the Akatsuki together, with Naruto using his newfound Saiyan - like strength and Goku using some ninja - inspired moves.
One possible plot could be that Naruto, as Goku's brother, has to learn the ways of ki while also maintaining his ninja skills. Maybe they team up to fight a common enemy that threatens both the ninja world and the Dragon Ball universe.
In a 'Naruto descendant of Goku' fanfiction, the plot could involve the discovery of a hidden bloodline in the Naruto universe that is related to Goku. This descendant might initially be an outcast because of their strange powers. However, as the story progresses, they start to show the true potential of their combined heritage. They could teach the ninjas about ki control, which is similar to chakra control in some ways. And in turn, they learn about the complex political and social structures of the ninja world from Naruto and others.
Well, it could be that Goku somehow ends up in the Naruto universe and has a son with a female character there. And this son has both the powers of a Saiyan like super strength and the ability to use chakra for jutsus. Maybe he's an outcast at first because of his strange powers but then becomes a hero.
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.