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.
Sasuke could be an alternative. He has strong ninja skills and a deep understanding of the ninja world. His experiences have made him grow into a very capable person, and his Sharingan gives him an edge in combat and strategic planning.
Even Naruto himself could be a subject of this 'evil Hokage' concept in fanfiction. Maybe he is possessed by some dark entity or has a major change of heart due to some extreme event. This would completely change his character and turn him into an evil Hokage, which would be a very interesting and unexpected twist.
Shikamaru is another possibility. He is known for his strategic mind. As Hokage, he could use his intelligence to make wise decisions for the village. He may not have the brute strength of Naruto or Sasuke, but his ability to plan and analyze situations would be invaluable in leading Konoha.
Sadly, I have no idea who penned 'the eighth man novel'. There are so many novels out there that it's difficult to know every author. You could also ask in a local bookstore or a reading group. Maybe someone there has read it and can tell you who the author is.
His friends like Sakura and Shikamaru would surely support him. Sakura, with her medical skills, could be an important part of his regime, providing healthcare for the ninjas. Shikamaru, being intelligent, could offer strategic advice. Also, the younger generation of ninjas who have been inspired by Naruto would be his strong supporters, as they believe in his leadership and the new direction he could take the village in.
Sasuke could also be a candidate in some fanfics. He has his own set of powerful abilities and a complex personality. A story could be written where he decides to take on the role of Hokage at a young age to bring about change in the village in his own way, perhaps using his Sharingan and new techniques he develops.
Sasuke could be a great choice. He has powerful abilities and a complex past. His experience as an avenger and then his redemption arc gives him a lot of depth. He has also learned from Naruto and has a different perspective on leadership. He could bring a more strict and strategic approach to being Hokage compared to Naruto.
It could be the First Hokage, Hashirama. Naruto would be amazed by his powerful Wood - Style jutsu and his ability to create the village. He could learn about the original ideals behind the Hidden Leaf from Hashirama.