Well, a plot might be that Naruto is experimented on by Orochimaru. Orochimaru, always interested in powerful abilities, tries to implant the Sharingan into Naruto. Naruto initially struggles with this new power as it's not native to him. But with his strong will, he begins to master it and uses it in ways no Uchiha has before. He could combine the Sharingan's visual prowess with his Rasengan, creating an even more powerful attack. For example, he might be able to see the chakra flow within an enemy more clearly with the Sharingan and then direct his Rasengan to target the weakest points.
One plot idea could be that Naruto is on a mission and stumbles upon an ancient Uchiha artifact that somehow bestows the Sharingan upon him. He then has to quickly learn to control it while his friends are both amazed and a bit wary. Another could be that during a battle with an unknown enemy who has the power to transfer abilities, Naruto ends up with the Sharingan. This leads to him exploring the new abilities in unique ways, like combining Rasengan with Sharingan - enhanced perception.
One possible plotline could be Naruto suddenly gaining the Sharingan through some mysterious jutsu accident. With the Sharingan, he could quickly learn new techniques and have enhanced perception. Combined with the Kyuubi's power, he might become an almost unbeatable force. For example, he could use the Sharingan to better control the Kyuubi's chakra flow, making his attacks more precise and powerful.
One possible fanfiction could be that Naruto is on a mission and encounters a powerful Uchiha who, instead of killing him, transfers his Sharingan to Naruto for some mysterious reason. Naruto then has to learn to control this new power while still maintaining his own unique ninja style.
In some fanfictions, Naruto gets the Sharingan as a gift from a dying Uchiha. This Uchiha, realizing Naruto's importance in uniting the ninja world, gives him the Sharingan. Naruto then uses it to understand the Uchiha's pain better and tries to bridge the gap between the Uchiha and the rest of the village. He also has to train hard to master the different levels of the Sharingan, like the Mangekyo Sharingan which comes with its own set of risks and rewards.
A possible plot could be a time - travel scenario. Hana and Naruto are sent back in time to the era when the Sharingan was first created. They have to figure out how to get back to their own time while also dealing with the power struggles and conflicts of that era. Hana's Sharingan becomes a key factor in their survival, as they use it to outwit powerful enemies and make allies among the ancient clans.
A plot could be that a rogue ninja steals the secrets of both the Sharingan and Byakugan and tries to create an army of super - ninjas with artificial versions of these eyes. The main characters then have to track him down and stop him before it's too late.
One plot idea could be that Naruto discovers an ancient scroll that reveals a way to obtain the Rinne Sharingan. This new power then causes a rift in the ninja world as some fear his newfound strength while others see it as a way to finally achieve peace. He has to struggle with mastering this power while also dealing with the political implications.
One interesting plot could be that Evil Naruto uses his Mangekyou Sharingan to manipulate the memories of the villagers. He makes them believe false things about their past and present, causing chaos in the village. For example, he could make them think that their friends are enemies, turning the village against itself.
One possible plot could be that Naruto, through some mysterious means, is given Sasuke's Sharingan. He then has to learn how to control it quickly as it starts to affect his perception of the world. He might see things in a different way, like being able to detect enemies more easily. Another plot could involve Naruto using the Sharingan to understand Sasuke better, seeing his memories and the pain that led him to become the way he is.
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.