A really interesting plot could be Naruto traveling back in time to the era before he was born. He could meet his parents and other important figures in the village's history. This would give him a chance to understand the roots of the village better and also learn some new jutsu or strategies that he could bring back to his own time to make the Hidden Leaf even stronger as a Hokage.
Rock Lee. He's often overshadowed by the main characters but he has a lot of potential. In a fanfic, he could be Naruto's right - hand man in training the new generation of shinobi. His unique fighting style and determination could inspire the young ones and he could also be a great help in protecting the village during tough times.
One idea could be a fanfic where the 7th Hokage, Naruto, has to face a new and powerful enemy from a hidden land that was previously unknown. This enemy has a unique jutsu that can nullify Naruto's chakra. Another idea is a story about Naruto's daily life as Hokage, dealing with the paperwork while also trying to find time for his family.
Maybe the new Hokage is faced with a crisis within the village. For example, there is a rift between different ninja clans, and the Hokage has to use his/her diplomatic skills to bring peace. They could start by holding clan meetings and listening to each clan's concerns.
One idea could be focusing on how the Sixth Hokage deals with new threats from outside the village. For example, a long - lost clan with a powerful and dangerous jutsu resurfaces. The Sixth Hokage has to use both diplomacy and strength to handle the situation.
One idea could be exploring the Godaime Hokage's early days in the role. Maybe she has to deal with a new and unexpected threat to the village that tests her leadership in ways she hadn't anticipated. Another could be a story where she has to make a difficult decision regarding the future of a young ninja with a troubled past, balancing the village's safety and the ninja's potential.
One idea could be Naruto facing a new and powerful enemy that challenges the very foundation of the Hidden Leaf Village. This enemy might be a rogue ninja with a grudge against Naruto for becoming the Sixth Hokage. Another plot could involve Naruto trying to implement new policies in the village but facing opposition from the traditionalist shinobi. For example, he might want to change the way chunin exams are conducted to be more inclusive, but the old - school ninja don't like the changes. Also, a plot could revolve around Naruto having to deal with a mysterious disease that is affecting the ninja in the village and he has to find a cure while still maintaining his duties as Hokage.
One idea could be exploring how the Sixth Hokage deals with the remaining threats from the Akatsuki. Maybe some members who were thought to be dead actually survived and are plotting revenge. Another could be focusing on the internal politics of the village. As the Sixth Hokage, there would be a lot of pressure to make decisions that satisfy different clans and factions within Konoha. Also, the Hokage could be involved in training a new generation of ninja with unique abilities, passing on the wisdom and skills Naruto has taught him.
One idea could be exploring the hidden powers within the Uzumaki clan that Naruto has yet to fully discover. Maybe there are ancient seals or techniques passed down only within the clan that could give him an edge in battles. Another plot could revolve around Naruto finding long - lost relatives from the Uzumaki clan who have been in hiding all this time and they bring with them new knowledge and skills. Also, a fanfic could focus on the Uzumaki clan's history during the time before Konoha was founded and how their actions influenced the future ninja world.
One idea could be exploring Naruto's relationship with his parents during his childhood if they were still alive. Maybe showing how Minato and Kushina would train him and the family adventures they'd have in Konoha.
One idea could be Naruto going on a secret mission in a hidden land not yet explored in the original series. Maybe he discovers a new type of chakra there.