He might become more brooding. The Uchiha are known for their intense emotions, and Naruto could inherit some of that. He may not be as openly optimistic as he was originally. Also, his sense of justice could be more influenced by the Uchiha's view of power and honor.
Naruto would likely be more in - touch with his Sharingan powers and the abilities that come with being an Uchiha. This could make him more of a strategic fighter rather than relying solely on his Uzumaki - style brute force. His relationships would also change. He might be more drawn to Sasuke as they now share an even deeper connection through their Uchiha heritage. And he might have a different attitude towards the village elders, especially if he discovers secrets about how they treated the Uchiha in the past.
The story would change drastically. Naruto's identity as a descendant of Madara would immediately put him at odds with some in the village who still fear the Uchiha. His journey to become Hokage would be even more challenging as he has to prove that he's not going to follow in Madara's footsteps. Also, his training might take a different route. He could be taught some ancient Uchiha techniques by an unexpected mentor, perhaps an old Uchiha who has been in hiding.
His relationship with Sasuke would become extremely complex. Sasuke, as an Uchiha, might have mixed feelings. On one hand, he could see Naruto as a link to the past of his clan through Madara. On the other hand, he might be wary of Naruto having Madara's essence. They might have to re - evaluate their rivalry and friendship.
The plot would change drastically. For one, the Uchiha massacre might not have happened as Naruto could have influenced Madara to prevent it. Also, Naruto would have had access to Uchiha knowledge and techniques from a young age. This would make him even more powerful. And his relationship with Sasuke would be more complex as they would be related through Madara.
Well, in such a fanfiction, Madara's training might enhance Naruto's physical strength. He could teach Naruto some advanced Uchiha techniques which Naruto can combine with his own Uzumaki powers. For example, Naruto might learn better chakra control from Madara, enabling him to use his Rasengan more effectively and with less chakra waste.
His relationship with Sasuke would be completely different. Instead of being rivals, they could become brothers. They would train together, share secrets, and support each other in a way that they couldn't in the original story. Naruto would also have a closer bond with Itachi, who might see Naruto as a new hope for the clan and mentor him.
His fighting style would likely incorporate more fire - based jutsu. Since the Uchiha are known for their fire - style techniques, Naruto would be trained in those from a young age. He might also use Sharingan - like abilities, even if it's not the real Sharingan. For example, he could develop a way to predict his opponents' moves more accurately, similar to how the Sharingan works.
His relationship with Sasuke would be really interesting. Since Sasuke has his own complex connection to the Uchiha clan and Madara, Naruto becoming a Madara fan could either bring them closer together in understanding the Uchiha's past or drive them further apart if Sasuke doesn't agree with Naruto's new - found admiration. Maybe Naruto would start to push Sasuke towards a more 'Madara - like' view of power and revenge.
If Naruto were born an Uchiha, his relationship with Sakura might be affected. Sakura might be more drawn to him initially because of the allure of the Uchiha clan. However, Naruto might be more focused on restoring the Uchiha name and proving that they are not all bad. His relationship with the villagers would be complex. Some would be fearful, while others might hope that he could use his Uchiha powers for the good of the village.
If Naruto becomes Madara Uchiha in fanfiction, it could drastically change the plot. Firstly, the relationships would be turned upside down. Naruto's friends might see him as an enemy, especially Sasuke who has a complex relationship with the Uchiha legacy. The power dynamics in the ninja world would also shift. Naruto, with Madara's power and knowledge, could either rule with an iron fist or try to reshape the world in a more extreme way compared to his original goal of peace. And the Akatsuki's plans would likely be disrupted as Naruto, in Madara's form, might have different motives regarding the tailed beasts.
Naruto might become more conflicted. Since Madara had some extreme views, Naruto would have to grapple with those ideas. He could become more secretive as he tries to understand Madara's motives better without alarming his friends. For instance, he might start training alone more often to study Madara - inspired techniques.