There could be a fanfiction where Madara and Naruto time - travel. They go back to the era before the great ninja wars and try to prevent all the tragedies from happening. This would involve them working together and facing many challenges along the way.
Another great concept for a Madara and Naruto fanfiction is a story where Madara is re - incarnated in a different world, and Naruto somehow follows him there. In this new world, they have to deal with different rules and powers, and their relationship evolves in unexpected ways.
In some fanfictions, Madara trains Naruto in the art of swordsmanship. Since Madara was a formidable warrior, he could pass on his skills. Naruto, who is mainly known for his ninjutsu and taijutsu, might discover a whole new combat style under Madara's tutelage. This could lead to some epic battles where he surprises his enemies with his newfound skills.
A great 'Naruto fem Madara' fanfiction could revolve around fem Madara being a mentor to Naruto. Instead of the usual antagonistic relationship that Madara has in the original series, she could use her powerful skills and knowledge to train Naruto. This would give Naruto a different kind of training experience and also allow for some unique character development for both of them as they navigate this new dynamic.
In some fanfics, Madara and Naruto could have a mentor - mentee relationship. Naruto, always eager to understand different perspectives, tries to learn from Madara's vast knowledge of the shinobi arts and history. This could lead to some really cool battle scenes where Naruto combines his own unique skills with the ancient techniques Madara teaches him.
An interesting idea is that when Madara is sealed, his chakra is spread across the ninja world. Naruto has to go on a journey to collect all these fragments of chakra to prevent Madara from ever being resurrected. Along the way, he meets different clans who have been affected by Madara's actions in the past and they either help or hinder his quest.
Another interesting concept is the idea of Madara's eyes having a sentient will of their own. In the fanfiction, the eyes could influence the character who possesses them, sometimes for good and sometimes for bad. It would create an internal struggle within the character as they try to maintain their own will while also dealing with the desires of Madara's eyes.
One interesting concept could be how Madara's reincarnation might change the power dynamics in the Naruto universe. For example, if he is reincarnated with some of his past memories intact, he could use that knowledge to his advantage in new and unexpected ways.
Another plot could be a time - travel scenario. The female Naruto is sent back in time and meets a younger Madara. She tries to change his path to prevent the future disasters he causes. In the process, she has to convince him to trust her, and they gradually develop a deep bond as she shows him a different way of seeing the ninja world.
One interesting plotline could be Naruto discovers a new form that gives him an edge over Madara. For example, a form that allows him to nullify Madara's Sharingan abilities. Another could be Madara having a change of heart due to Naruto's unwavering belief in him. Maybe he starts to question his own motives for destruction.
A possible interesting plot could be Naruto using Madara's body to face off against the Akatsuki. They might be confused as to why 'Madara' is acting so differently.
One interesting idea could be exploring the power dynamics between Madara and Naruto. Since Madara is a very powerful and experienced shinobi, and Naruto has his own unique strength. Their interactions might lead to some intense and unexpected plot developments.