Well, a great storyline might be Naruto and Sarutobi Sensei going on a secret mission together. Maybe they have to retrieve a powerful and dangerous artifact before it falls into the wrong hands. Or perhaps a story where Sarutobi Sensei reveals to Naruto some hidden secrets about his family that have been long forgotten. Also, a story where Sarutobi Sensei uses his experience to help Naruto deal with some political unrest within the Hidden Leaf Village would be quite engaging.
A possible storyline is that Sarutobi Sensei, seeing Naruto's potential, decides to train him in a special form of chakra control that only he knows. This could lead to Naruto developing a new and powerful technique. Another idea is a story set during a time when the village is under attack and Sarutobi Sensei entrusts Naruto with a crucial task that could save the village. There could also be a fanfiction where Sarutobi Sensei and Naruto have to solve a mystery that has been plaguing the village for ages.
One interesting storyline could be Naruto learning some ancient and forgotten jutsus from Sarutobi Sensei. This could involve Sarutobi Sensei passing on his vast knowledge of unique techniques that were lost over time. Another could be a time - travel story where Naruto goes back in time and meets a young Sarutobi Sensei, and they team up to face a common enemy. It could also be a story where Sarutobi Sensei trains Naruto in the art of leadership, much like he did for the previous generations in Konoha.
One way is through joint training sessions. Sarutobi Sensei could push Naruto to his limits and in the process, they would learn more about each other's strengths and weaknesses. Also, they could be put in a situation where they have to rely on each other completely, like being trapped in a dangerous genjutsu. Sarutobi Sensei could then use his wisdom to guide Naruto out, strengthening their relationship. Another aspect could be Sarutobi Sensei introducing Naruto to important figures from his past, which would give Naruto more context about his sensei and bring them closer.
A great storyline could be about Gai Sensei sharing his life stories with Naruto. How he overcame his own weaknesses and challenges in his youth. This would not only be inspiring for Naruto but also give readers a deeper understanding of Gai Sensei. Naruto could then use these stories as motivation in his own journey to become stronger and protect the village.
One possible plotline could be Sarutobi mentoring Naruto more closely. Since he's alive, he could pass on even more of his wisdom and jutsu knowledge to Naruto. For example, he might teach Naruto some of the more secretive fire - style jutsu that only he knows.
One interesting plotline could be Naruto using his unique experiences as a former student to develop new and unorthodox teaching methods. For example, he might incorporate his own journey of learning difficult jutsus into his lessons, making it more relatable for his students.
One interesting 'naruto sensei fanfiction' story could be about Naruto teaching a new generation of ninja unique jutsu. For example, he might teach them a special combination of his Rasengan and Shadow Clone techniques. Another could be Naruto as a sensei during a time of peace, and he has to deal with the daily antics of his over - enthusiastic students. There could also be a story where Naruto as a sensei discovers a hidden talent in a seemingly ordinary student and helps that student reach their full potential.
In this fanfiction scenario, Naruto might learn unique chakra control techniques from Sarutobi. Sarutobi, being an experienced ninja, could teach Naruto how to better manage his large chakra reserves. This would lead to Naruto being able to perform jutsus more efficiently and with less waste of chakra.
I really like 'Sarutobi's Unseen Trials'. In this fanfiction, it focuses on the political aspects that Sarutobi had to deal with in the Hidden Leaf Village. It gives a new perspective on his leadership and the difficult decisions he had to make.
Perhaps in this fanfiction, Sarutobi is trapped in a genjutsu created by a rogue ninja. Naruto, being highly resistant to genjutsu due to his Uzumaki blood, manages to break into the genjutsu world. There, he has to fight his own inner demons as well as the rogue ninja's illusions to free Sarutobi.
One idea could be exploring the early days of the Sarutobi clan. Maybe show how they developed their unique jutsu. Another could be a story centered around a young Sarutobi clan member who has a rare ability and must prove themselves in the Hidden Leaf Village.
One consequence could be that the village runs more smoothly. With the paperwork out of the way, decisions can be implemented faster.