Sasuke Uchiha also remains a popular character. His complex relationship with Naruto is a central part of the original series, and in fanfiction, it's often explored further. The reincarnated Naruto might have a different approach to dealing with Sasuke's issues and their rivalry.
One interesting plotline could be the main character using their prior knowledge to quickly master jutsu that Naruto struggled with in the original story. For example, they might be able to perform the Rasengan much earlier and with more finesse, which would change the way early battles play out in the Naruto universe.
The Legend of Uzumaki Hiroto was a derivative work of Naruto, which told the story of Uzumaki Hiroto's growth and the stories of other characters. Uzumaki Boto Legend was different from the original Naruto Naruto Shimbun Legend, so it was considered an independent manga.
It depends on the specific plot of the fanfic. Sometimes he could be on a secret mission, in a hidden village, or facing a new challenge in an unknown location.
Well, he could start a family with Hinata and have lots of kids, passing on his Uzumaki bloodline. Then, he could encourage his friends who have some Uzumaki connection, like Karin, to also have families and pass on their Uzumaki genes. He could also set up a school or training center in the Uzumaki land, teaching the Uzumaki ways of life and ninjutsu, which would attract orphans or those who want to be part of the Uzumaki clan.
He could be reincarnated as one of the Uchiha clan members. This would be really interesting as he would have to deal with the Sharingan and the Uchiha's history. He might even change the fate of the clan.
They are not appropriate. The Naruto series is known for its action, adventure, and positive themes. Lemon fanfics that may contain sexual or explicit content are not in harmony with the family - friendly nature of the original Naruto work. It's better to focus on fanfics that respect the original themes and values of the series.
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.
Naruto could also express his love in a more playful way. He might tease the reader a lot but in a loving manner. And he'd bring her little gifts, like a special kunai he found on one of his adventures or some flowers from the outskirts of the village. He'd want to make the reader laugh and feel special all the time.
Well, in the fanfic world, the author might have created a backstory or a set of rules. It could be that Tsunade's family lineage has been clearly defined in a way that excludes her from being considered an Uzumaki. Naruto, being a character within that fan - created world, has to abide by those rules. For example, perhaps her family tree has been traced and it shows no connection to the Uzumaki clan, so Naruto simply can't claim her as one.