Perhaps Madara's grandfather was a diplomat of sorts for the Uchiha. He might have been involved in negotiations with other clans or villages. This would explain how the Uchiha managed to hold their ground and gain influence in the ninja world at that time. He could have used his wisdom and charisma to form alliances and avoid unnecessary conflicts.
It's also likely that Madara's grandfather was a seer or had some sort of prophetic ability. He could have foreseen the future of the Uchiha clan, including Madara's rise and fall. This would have influenced the clan's decisions and actions over the generations. For example, he might have left behind prophecies or warnings that the clan either heeded or ignored, which in turn affected their fate.
Another idea is that the fanfic delves into a what - if scenario. What if Naruto's grandfather had been able to change Madara's path? This could lead to a completely different Naruto - verse, where the Uchiha clan's history and the overall power balance in the ninja world are altered. The fanfic could then explore how Naruto's life and his journey as a ninja would be different in this alternate reality.
He could be a powerful and respected shinobi from the Uzumaki clan. Given the Uzumaki's reputation for strong chakra and unique abilities, Naruto's grandfather might have been a key figure in the clan's history.
One implication could be in terms of Naruto's power. Since Madara was extremely powerful, Naruto might inherit some latent Uchiha abilities. Also, it could change Naruto's view of the Uchiha - Senju conflict. He might see it from a more personal perspective.
In fanfiction, the possibilities are endless. Regarding Madara Uchiha being Naruto's grandfather, it could be a really cool and unique take. Maybe the fanfic writer has a great plot in mind where this relationship changes the whole Naruto story. For example, it could influence Naruto's powers, his understanding of the Uchiha clan, or even how he views the history of the ninja world. But of course, this is just a fanfiction idea and has no basis in the original Naruto plot.
I'm not entirely sure if there is a specific fanfiction with Naruto's grandfather being Madara Uchiha. But in the realm of fanfiction, anything is possible. Writers might be intrigued by the idea of mixing Naruto's story with the power and history of Madara Uchiha in such a way. It could lead to some really interesting plot developments, like how Naruto's character might be different growing up with such a powerful and infamous figure as his grandfather in the backstory of the fan - created world.
Madara's grandfather could have had an impact on the clan's relationships with other ninja groups. If he was respected by other clans, it would have improved the Uchiha's standing in the ninja world. On the other hand, if he made enemies, it could have led to long - term rivalries and conflicts that Madara would have to deal with later. His actions and decisions in this regard would have shaped the Uchiha clan's place in the overall ninja society.
His grandfather could be a very strict and traditional ninja. He might have high standards for Naruto in terms of ninja skills and discipline.
Since Madara was very knowledgeable about the history of the ninja world, Naruto's training would include a lot of historical and cultural knowledge. This would give Naruto a broader perspective in battles. He would not only be physically strong but also be able to outwit his opponents with his knowledge. And Madara could introduce Naruto to some powerful allies or places that are related to the Uchiha heritage which could enhance his training.
It would be very different from the original Naruto story. Naruto might have access to some of the Uchiha secrets and powers much earlier. His view of the Uchiha clan and the history of the ninja world would be shaped by Madara's influence. Maybe he would be more powerful from the start, having inherited some of Madara's abilities or knowledge.
In this kind of fanfiction, Naruto might learn a lot of hidden family secrets. His grandfather could teach him some long - lost jutsu that was unique to their family. Maybe his grandfather would tell him stories about the early days of Konoha, which could give Naruto a new perspective on the village he loves so much.