A cool plot idea might be a Sharingan warrior from a different dimension coming into the main Naruto universe. This warrior has a unique way of using the Sharingan that no one in the main universe has seen before. They could either become an ally or a formidable enemy, depending on their motives. Their presence could disrupt the existing power balance and force the characters in the Naruto world to adapt and find new ways to combat this new threat or form new alliances with this strange visitor.
Another plot could revolve around a character who accidentally acquires the Rinne Sharingan and has to learn to control it while being hunted by various groups. Some might want to use the power for their own evil purposes, while others fear the unknown capabilities. This character could start as a relatively weak ninja but gradually become stronger as they master the Rinne Sharingan, forming alliances with unexpected characters along the way.
One idea could be that Naruto discovers a hidden Uchiha ancestor in his family tree. This could lead to the dormant Sharingan gene awakening in him. He then has to learn to control the Sharingan while still maintaining his own unique ninja abilities. Another plot could be that during a battle with a powerful enemy, Naruto is somehow merged with an Uchiha ninja, and as a result, he gains access to the Sharingan. He then uses it to gain new insights into his opponents' moves and strategies.
One idea could be a story where the protagonist discovers a new and unique power within the Mangekyou Sharingan that has been lost for generations. This power could give them an edge in battles against powerful foes like the Akatsuki. Another plot could revolve around a character who has to overcome the dark side effects of using the Mangekyou Sharingan, such as losing their sight at a faster rate. They could search for a way to counter this while still using the power to protect their village.
One idea could be a story where the Sharingan evolves to an ultimate form that gives Naruto unique powers. For example, he might be able to use it to instantly teleport to any location he has previously visited. This would add a new dimension to his fighting abilities and his ability to save his friends quickly.
Another plot could revolve around a character who has the Mangekyo Sharingan but is trying to hide it from both their allies and enemies. They fear the power it holds and the attention it might draw. As the story progresses, they are forced to use it in a crucial battle, and their friends then have to deal with the revelation and the potential danger it brings to the group.
Another plot idea is that Naruto gets a Sharingan in a parallel universe. In this universe, he has to learn how to control it quickly while also dealing with the different political situations. Since the Sharingan is so powerful, many might try to either use Naruto or take the Sharingan from him, creating a lot of action - packed and suspenseful situations.
One interesting plot idea could be a character from the Naruto world obtaining the Mangekyo Sharingan through some strange and unforeseen event. For example, Naruto himself could be exposed to a powerful Uchiha - related jutsu that accidentally gives him the Mangekyo Sharingan. This would completely change his power dynamic and how he approaches battles. He could then have to learn how to control this new power while still maintaining his own ninja way.
One interesting plot idea could be a story where a character with both Sharingan and Rinnegan has to face an ancient evil that threatens the entire ninja world. This character could struggle with the power and the different abilities of both eyes as they try to master them in order to defeat the enemy.
Perhaps Naruto gets the Sharingan in a different dimension where he has to adapt to this new power. He could face challenges like being hunted by those who want to steal the Sharingan from him. He might also discover new abilities within the Sharingan that are unique to him because he's not a pure - blooded Uchiha. For example, he could use the Sharingan to enhance his Sage Mode, seeing things more clearly and predicting attacks better.
One idea could be that the character with the Sharingan is banished due to false accusations of using its power for evil. He then has to journey alone, facing challenges and learning to control his power in new ways. Maybe he meets a group of outcasts who he befriends and together they fight against the unjust system that banished him.