Well, Naruto could go back in time and train his younger self. He'd be able to pass on all the skills and knowledge he has as the 6th Hokage. This would make his younger self much stronger and more confident much earlier in life.
They could go on adventures together. As the 6th Hokage, Naruto would have access to all kinds of resources and knowledge. Hinata, being his wife, could accompany him on some secret or important missions. For example, they might go to explore an ancient ninja ruin to find a powerful artifact that could help protect the village. Along the way, they would face various traps and enemies, and their love for each other would be tested.
Well, if Naruto becomes the 5th Hokage in fanfiction, he would surely bring a new energy to the village. He might start by reforming the ninja training system. Since he had a tough time growing up as an outcast, he'd make sure no kid in the village ever feels that way. He could also focus on better relations with other villages. Naruto's always been about peace and friendship, so he'd probably organize more joint ninja missions with other villages to build trust.
Maybe Naruto travels back to his own childhood days. He could use his knowledge as Hokage to help his younger self become stronger faster. He might also be able to prevent some of the hardships he faced, like not having enough food sometimes. This would not only change his own life but also the relationships he had with people like Iruka - sensei, who took him under his wing when he was a lonely kid.
Another idea for this fanfiction is that Naruto's time travel as the 6th Hokage could lead to him meeting his predecessors in a different way. He could learn new jutsu or leadership skills directly from them. For instance, he could have in - depth conversations with the 1st Hokage, Hashirama, about how to better manage the relationships between different ninja clans and build a stronger, more united village.
In this fanfic, Naruto might bring new policies to the village. He could focus on improving the relations between different ninja clans. For example, he might create more joint training programs for the Uchiha and other clans to heal the old wounds.
Naruto himself could be a likely candidate. Given his strength, leadership skills, and his dream of uniting the ninja world, he would make a great 6th Hokage.
Sasuke could also be a possibility for the 6th Hokage in the fanfic. He has grown stronger over the years and his unique perspective on the ninja world could bring new ideas to the leadership of the Hidden Leaf. He might start off as a controversial choice but prove himself through his actions in protecting the village and making tough decisions.
One possible plot could be that fem Naruto travels back in time to her younger self. She uses her knowledge as a Hokage to prevent certain tragedies. For example, she could stop Sasuke from leaving the village in the first place. This would change the whole course of events in the Naruto world.
Well, it could be that Naruto meets the Hokage in a different time - space. They might work together to change some important events in the history of the village. For example, preventing a great disaster or changing the fate of some important characters. And Naruto could learn a great deal from the Hokage's wisdom and leadership in this encounter.
If Naruto travels back to the past, his relationship with his parents would be completely different. He would finally get to meet them as an adult and be able to have proper conversations with them. He could share his experiences and they could give him advice from their own wisdom.