Well, in such a fanfiction, it might explore the power dynamics differently. Danzo, being a powerful figure, if he cares about Naruto, could offer Naruto unique training opportunities. This could lead to Naruto developing new skills and a different relationship with the village. It might also change how Naruto views the more shadowy aspects of the Hidden Leaf, since Danzo is associated with those elements.
One possible fanfiction idea could be that Danzo is forced into an arranged marriage with a female ninja from a powerful clan. She initially despises him because of his ruthless reputation but gradually discovers his complex motives and they develop an unexpected bond.
One possible scenario in a fanfiction could be that Danzo secretly admires a female ninja from a distance. Maybe she's a skilled healer in the village. He might be drawn to her kindness and the way she devotes herself to helping others, but his position and his secretive nature prevent him from expressing his feelings openly.
Maybe it's out of guilt. In the original story, Danzo has done some shady things that might have affected Naruto indirectly. So in fanfiction, he could care about Naruto as a way to make amends.
He'll likely lose his power and influence in the village. Once Naruto reveals his secrets, the villagers won't trust him anymore. His actions might be put on trial, and he could be exiled from the village.
It could mean that in the Naruto fanfiction universe, the Kyuubi (Nine - Tailed Fox) has some sort of emotional investment or interest in the stories being written about Naruto. Maybe the fanfictions explore aspects of their relationship in new and interesting ways that the Kyuubi, in the context of these fictional tales, is somehow aware of or involved in.
One way the Kyuubi can show it cares about Naruto fanfiction is by being a consistent and important part of the stories. If the Kyuubi is always there to support Naruto, either by giving him power or by sharing its wisdom, in various fanfiction scenarios, it indicates that it has a role to play and is interested in the development of the fan - created Naruto stories. Fanfiction often plays with the relationship between the two, and if the Kyuubi is actively engaged in these new storylines, it can be seen as caring about the Naruto fanfiction.
In the Naruto universe, while it's highly unlikely in the official canon, in fanfiction, anything can be made possible. The Sharingan is a kekkei genkai exclusive to the Uchiha clan. Danzo had Sharingan in his arm which he obtained through rather unethical means. For Naruto to get it from him in fanfiction, it could be written through some sort of experimental jutsu gone wrong or right. Maybe a jutsu that was meant to transfer power ended up giving Naruto the Sharingan. However, this would completely change Naruto's power dynamics and character arc as the Sharingan comes with its own set of abilities like the ability to copy jutsu, predict movements, and use genjutsu.
There's a fanfic where Danzo tries to manipulate Naruto for his own political gain. However, Naruto, being the perceptive character he is, quickly catches on. This leads to a battle of wits between them. In the end, Naruto uses his own brand of talk - no - jutsu to make Danzo see the error of his ways and they end up working together to reform the village's political system.
In a fanfic where Danzo gives Naruto the Sharingan, it could lead to a very different Naruto. Naruto might gain new abilities and a new perspective on the Uchiha. He could potentially master the Sharingan quickly with his strong willpower, but he would also have to deal with the dark side of the Sharingan, like the curse of hatred that often comes with it.