Well, Naruto's character would be severely altered. Danzo is all about the end - justifying - the - means type of person. Naruto would be trained in a very different way. He'd probably be more proficient in stealth and assassination techniques rather than the flashy jutsu he learned under Jiraiya. His sense of justice would be warped. Instead of believing in everyone and trying to save his enemies, he might be more inclined to eliminate threats preemptively, like Danzo. His relationships would also be affected. He might not have the same close - knit group of friends as he did in the original story.
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 also be due to Naruto's outcast status in the village initially. Danzo might think that banishing Naruto would be an easy decision as Naruto doesn't have many supporters at first. He might believe that by getting rid of Naruto, he can maintain the status quo in the village and prevent any disruptions that Naruto's presence might cause in the future.
His relationship with Sasuke would be very different. Instead of seeing Sasuke as a rival and a friend, he might view him as a potential threat to the village from the start. With Sakura, he may not be as friendly or protective. His bond with Kakashi would likely be non - existent or at least very strained, as Danzo and Kakashi have different outlooks. Naruto would probably be more isolated from his peers, as Danzo's upbringing would make him more guarded.
One possible motive could be to gain control over Naruto's power. Since Naruto has the Nine - Tails within him, Danzo might want to use that power for his own political or military gains. He's always been power - hungry and sees Naruto as a tool to achieve his goals of making Konoha stronger in his own way, which might involve more underhanded and controlling methods.
One possible motive could be revenge. Maybe the oc or someone close to the oc has been wronged by Danzo in the past. So, to seek justice, the oc decides to take him down.
Well, in some versions, Naruto might use his influence among the villagers. After Pain's attack, the village is in a state of rebuilding and re - evaluating. Naruto, being a hero, has the ears of the people. He could start by presenting evidence of Danzo's underhanded deals, like his connection to Orochimaru perhaps. Maybe he found some secret documents during the chaos that Pain caused, which link Danzo to unethical experiments or power - grabbing within the village.
A plot where Danzo fakes his death and teams up with Naruto undercover to take down a hidden threat to the village. They have to keep their alliance a secret from everyone, including the other village leaders. This creates a lot of tension and secrecy in the story.
Well, in such a fanfic, Naruto might turn against his friends. He could be made to use his power for Danzo's often shady purposes. For example, he might be forced to target those Danzo sees as threats to Konoha in a more brutal way than he normally would. His relationships would be severely damaged as his friends would be confused and likely try to stop him, not realizing he's been brainwashed at first.
One interesting 'Naruto Danzo Sensei' fanfiction could be about his early days as a ninja and how he developed his strict and secretive ways. It might explore his relationships with his peers at that time.