In terms of the overarching Naruto plot, they could have a major impact on the Akatsuki's plans. If the Akatsuki hears about an OC Uchiha with an activated Sharingan from birth, they might try to recruit them. This would put the OC in a difficult position, as they would have to decide whether to side with the Akatsuki or stay loyal to their clan and village. Their decision could change the course of many events in the Naruto world.
In a fanfiction, an OC Uchiha born with an activated Sharingan could face unique challenges. The Sharingan drains chakra, and being born with it activated might mean they have to learn early on how to manage their chakra levels more effectively. Also, they could attract unwanted attention, either from jealous clan members or from enemies who see them as a threat due to their special ability.
Perhaps in this fanfiction, Naruto being born an Uchiha means he has a natural rivalry with Sasuke from the start. Since they both have Uchiha blood, they might compete not just for power but also for the right to be the true heir of the Uchiha legacy. Also, his Uchiha lineage could attract the attention of Orochimaru, who might see Naruto as a new vessel with the potential of the Uchiha powers.
Well, the OC might try to prevent the Uchiha Massacre. Maybe they have a different view of the Uchiha compared to the Konoha leadership. They could try to convince the Uchiha to flee or negotiate with Konoha. If they have unique powers or knowledge, they could use it to expose the real motives behind the planned massacre and create a situation where the Uchiha are spared. This would completely rewrite the story of the Uchiha's downfall.
Well, one possibility is that he'd have the Sharingan from the start. He might grow up with different training methods, more focused on Uchiha techniques. Maybe he'd be more of an outcast in the village not just because of the Nine - Tails, but also because of the Uchiha's reputation. And his relationship with Sasuke would be completely different, perhaps they'd be rivals in a whole new way, competing over who is the true Uchiha heir in terms of power and abilities.
Well, if Naruto was born with the Sharingan, it would completely disrupt the original power dynamics. He'd have an edge in combat from the start. For example, he could quickly copy jutsu like Sasuke does with his Sharingan. This might make his early training with Iruka and Kakashi very different as he'd already have a powerful dojutsu at his disposal.
A plot twist could also involve her relationship with the other Uchiha members. Since Naruto is known for her strong will and determination, she might challenge the traditional Uchiha ways. For example, the Uchiha are often associated with revenge and a thirst for power. But she could try to change that mindset within the clan, causing a rift between those who want to stick to the old ways and those who are inspired by her new ideas.
In fanfiction, Naruto could get the Sharingan through a blood - related connection that is revealed later. For example, it could be discovered that he has some distant Uchiha ancestry that gets activated somehow. Maybe a powerful enemy's attack awakens this dormant Uchiha blood in him, and as a result, he develops the Sharingan. It could also be that a powerful sage or a new character uses their own unique powers to bestow the Sharingan upon Naruto for a specific purpose.
To develop a great plot for a Naruto male Uchiha OC fanfiction, think about the big picture of the Naruto world. Your OC could be in the middle of a power struggle between the villages. Since he's an Uchiha, he might be seen as a threat or an asset. You can also involve love interests. Maybe he falls in love with a character from a different village which complicates things. And don't forget about his growth as a ninja. He could start as a weakling but through hard work and determination, he becomes a powerful force in the ninja world, all while dealing with the burden and power of being an Uchiha.
One possible plot could be that Naruto discovers he has some Uchiha blood in him. This revelation would change his perspective on himself and his place in the ninja world. He might then start to train more intensively to master Uchiha abilities.
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.