In fanfiction, anything can happen. The author might create a crossover scenario where Naruto somehow gets the Sharingan and ends up in the Fairy Tail universe. It could be due to some magical or scientific experiment gone wrong or right, depending on how the story is framed.
One potential plotline could be Naruto using his new powers to finally bring true peace to the ninja world. He could use the Sharingan to understand the root causes of conflicts by seeing through people's true intentions and the Rinnegan to reshape the world in a more harmonious way.
Perhaps Naruto gets the blue Sharingan as part of a forbidden ritual that was meant to save the Hidden Leaf Village from a powerful dark force. This would lead to him being shunned by some villagers who fear his new, unknown power. He would then have to prove himself and his intentions with the Sharingan. Also, it could be that the blue Sharingan is a key to unlocking a hidden dimension that holds the secrets to ultimate ninja power, and Naruto embarks on a journey to explore this dimension.
Yes, there are likely some fanfics out there with this concept. The Naruto fandom is vast and creative, and some authors might come up with the idea of Naruto having a blue Sharingan for the sake of unique storylines, crossovers, or just to explore different power combinations within the Naruto universe.
Yes, in some fanfictions, Naruto can be depicted as having the Sharingan. Fanfiction writers often like to play with different character abilities and combinations, so it's not uncommon to see Naruto with the Sharingan in their creative works.
The Sharingan in such a fanfiction could be used as a tool for a Fairy Tail character to gain an edge in their battles. They might initially struggle to control it, but as they learn more about it, they become a formidable force. For instance, they could use the Sharingan's genjutsu abilities to deceive opponents in the Fairy Tail battles.
Sakura could be an unexpected character to have the Sharingan. It would completely change her character dynamics. She could use it to enhance her medical ninjutsu, seeing the internal body structure more clearly. Also, she could become a more formidable fighter, using Sharingan - based genjutsu to her advantage.
One interesting storyline could be Naruto using the Sharingan to copy the magic of Fairy Tail wizards. He could then combine his ninja skills with the copied magic, creating unique fighting styles. For example, he might copy Erza's requip magic and use it to quickly change his ninja tools during battle.
It could be Sasuke. In many Naruto - related stories, Sasuke has the Sharingan and is often the target of others' tricks or manipulations due to his complex personality and his power.
A fanfiction could be set in an alternate universe where the Sharingan and Byakugan have different powers than in the original Naruto series. For example, the Sharingan could be used to directly communicate with the spirits of the dead, and the Byakugan could see into different dimensions. A young ninja discovers these new abilities and has to use them to save his village from a mysterious threat.