A great plot could be that a powerful fox entity chooses Naruto and Sasuke as its vessels. They have to fight for control over their bodies while also trying to understand the motives of the fox. This leads to a lot of internal conflict within them as they struggle between their own wills and the power of the fox.
One idea could be that Naruto and Sasuke discover a hidden fox spirit realm. In this realm, they have to work together to solve puzzles and face challenges set by the fox spirits. Their bond is tested as they encounter illusions related to their past traumas.
Perhaps Naruto discovers a hidden power within himself that can only be unlocked with Sasuke's help. As a wolf, Sasuke has a connection to the moon, and Naruto's fox powers are related to the sun. Their combined powers are the key to saving their world from an impending doom.
One interesting plot idea could be that in a world where Sasuke is a wolf and Naruto is a fox, they are forced to team up against a common enemy that threatens their respective clans. They start off distrusting each other but as they face challenges together, they learn to rely on one another's unique abilities.
One idea could be that Naruto and Sasuke are transported to the DxD world and they have to learn the new rules and powers there. They might team up with some of the DxD characters to face a common enemy.
One idea could be a story where Ino uses her mind - transfer jutsu to enter Sasuke's mind during a crucial moment when he's on the verge of succumbing to the darkness again. Naruto, realizing what Ino is doing, tries to help her from the outside. They discover memories in Sasuke's mind that no one knew about, and these memories are the key to bringing Sasuke fully back to the side of the village.
Perhaps there is a prophecy that a union between them would result in a special child. They initially resist the idea but as the pregnancy progresses, they start to embrace the new situation and work together to protect the unborn child from those who might want to harm it. They also have to face the challenges of changing their relationship from rivals to co - parents.
One idea could be a fanfiction where Naruto and Sasuke have to team up again to face a new threat from an ancient evil that has been awakened. They have to put aside their past differences completely and combine their powers in a new way. For example, Naruto could use his Sage Mode along with Sasuke's Rinnegan to perform a super - powerful jutsu.
In a fanfiction, there could be a story where a mysterious enemy targets Sasuke, Naruto and Sakura specifically because of their unique bond. The three of them then have to go into hiding and figure out who the enemy is and what they want. Along the way, they rely on each other's strengths and grow even closer as friends.
In some fanfictions, they meet in a situation where Sasuke has lost his memory. Naruto then takes it upon himself to help Sasuke regain his memories and in the process, they go on various adventures together, facing different challenges that test their bond all over again.
One idea could be Naruto and Sasuke teaming up to face a new, powerful and ancient threat that even the combined might of the Hidden Villages can't handle easily. They have to use their unique skills and the bond they've reforged as Hokage and his equal.
One idea could be that Naruto and Sasuke find a baby on one of their missions. They then have to figure out how to take care of it while also dealing with the political implications in the ninja world. Maybe the baby has some special power that attracts the attention of both friends and foes.