Maybe he travels back to the time when the ninja clans were first forming. He could influence the way the ninja system is developed, for example, by promoting more peaceful co - existence among clans from the start. This would lead to a very different Naruto world where the concept of hidden villages might not even exist in the same way.
One interesting plot idea could be exploring how the reincarnation affects Naruto's relationships. Maybe his friends start to notice strange changes in him that are related to the Rikudou Sennin's past. Another idea is that the reincarnation gives Naruto new powers that he has to learn to control quickly in order to face a new, powerful enemy. Also, the story could focus on how Naruto discovers the full history of the Rikudou Sennin through his reincarnation experiences.
One interesting plot idea could be that the reborn Rikudou Sennin has partial amnesia. He remembers his great power but not how to fully control it. This leads to him accidentally causing chaos in the ninja world as he tries to relearn his abilities. Another idea is that he is reborn into a different clan than his original one, and has to deal with the cultural and political differences while still having his old soul's knowledge.
One interesting plot could be that Rikudou Sennin is reborn into a time when the ninja world is on the verge of a new, unknown threat. He has to quickly regain his powers and knowledge to guide the new generation of ninjas, like Naruto and his friends, to face this threat. Maybe he has lost some of his memories in the rebirth process, adding an element of mystery and self - discovery to the story.
One interesting story could be about Rikudou Sennin's early days and how he discovered his powers. Maybe it shows his first encounters with the chakra beasts.
In a fanfiction, the Rikudou Sennin could have foreseen a future threat that neither the Naruto world nor the DC universe could face alone. So, he sends Naruto to the DC universe to recruit the Justice League. Naruto has to convince the skeptical heroes to come back with him to his world. Once there, they find that the threat is a combination of powerful ninja - based villains and some of the DC super - villains who have joined forces. They must then work together, with Naruto and the Justice League using their respective powers and skills to defeat this new alliance.
Yes, in some fanfictions, Naruto can be depicted as the Rikudou Sennin. Fanfiction writers often take creative liberties and come up with unique storylines where Naruto might inherit the powers or even be reincarnated as the Rikudou Sennin to explore different plot developments and character arcs.
One implication is that Naruto would have an extraordinary amount of power. He could potentially reshape the ninja world more easily. For instance, he might be able to end all wars and conflicts with a snap of his fingers.
For Naruto, if Rikudou Sennin travels back in time, he could potentially train Naruto earlier. This would make Naruto much more powerful at a younger age and might change the way he faces his enemies like Sasuke. Naruto could also learn some ancient jutsu directly from the Rikudou Sennin.
One interesting crossover could be a story where the power of Rikudou Sennin from Naruto is somehow combined with the magic in Fairy Tail. Maybe a character from Fairy Tail discovers an ancient artifact that has the power of the Rikudou Sennin and has to learn how to control it. This could lead to new and unique magical abilities for that character.
In fanfiction, the idea of Naruto being the son of Rikudou Sennin can be really interesting. It could change so many aspects of the story. For example, his relationship with other characters like Sasuke might be different. His power growth could also be explained in a whole new way. But we have to remember that this is just a fan - created concept and not part of the original Naruto story. The original story has its own well - established plot and character relationships that are different from this fanfiction idea.