One idea could be that the male OC is reborn into the Uzumaki clan during a time of great turmoil. He could use his knowledge from his past life to help the clan survive and thrive. Maybe he knows about upcoming threats and can prepare the Uzumaki for them.
One interesting plotline could be the main character, reborn as Naruto, using modern knowledge to change certain events in the Naruto universe. For example, they might introduce new training methods early on to make Naruto stronger faster.
Kakashi is another popular character. Fans often like to see how he reacts to the reborn Naruto. Maybe the reborn Naruto can teach Kakashi something new, or they can work together in a different way compared to the original story. His cool and mysterious personality adds an interesting dynamic to the fanfiction.
He might also have the power to sense chakra more acutely. This would help him in detecting enemies from a distance, finding hidden traps that are chakra - based, and also in understanding the flow of chakra within his own body better. He could use this power to train more effectively and also to teach others about chakra control.
One of the main themes is love. Not just the mother - son love between Naruto and Kushina, but also how Kushina's love for Naruto can be a driving force in the story. For instance, in some fanfics, Kushina's love gives Naruto the strength to overcome great challenges. Also, the theme of sacrifice is common. Kushina sacrificed herself for Naruto, and fanfics often expand on this idea, showing how Naruto honors her sacrifice and what it means for his character development. In addition, there's often a theme of discovery, where Naruto discovers more about his mother and his own identity as an Uzumaki.
One interesting fanfiction could be about Mit Uzumaki and Naruto Uzumaki teaming up to face a new, powerful enemy that the Hidden Leaf Village has never seen before. They could combine their unique skills and family powers to protect the village.
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.
Their rebirth could lead to a new era of cooperation. The Uzumaki and Senju clans have always had a certain connection, but with Naruto and Hashirama reborn, they could work together more closely. This could involve joint training programs for the younger generations, where Uzumaki kids learn about Wood Style from the Senju, and Senju kids learn about sealing from the Uzumaki. It would also likely lead to a more united front against common enemies in the ninja world.