The Hokage at the time of the banishment would be a central character. If it's Tsunade, she might have been pressured into banishing Naruto but later regrets it. Shikamaru, being one of Naruto's friends and also a strategic thinker, would probably be involved in the efforts to bring Naruto back. He could come up with plans to convince Naruto to return. Hinata, who has always had feelings for Naruto, would surely be part of the story. She might be the one to reach out to Naruto on an emotional level and persuade him to come back.
Sakura would likely be involved. She might be one of the first to realize the village made a mistake in banishing Naruto. Kakashi too, as he has always been a mentor figure to Naruto. He could be torn between his loyalty to the village and his belief in Naruto. Sasuke could also play a role. Maybe he hears about Naruto's banishment while on his own journey and decides to help bring him back when he realizes Naruto's importance to the village and to himself.
Obviously, Naruto is the central character. But other characters like Sasuke could also be involved. Sasuke might be torn between his loyalty to Konoha and his friendship with Naruto. He could either try to bring Naruto back or join him in his exile.
Sasuke would likely be involved. He has his own issues with Konoha and might side with Naruto, either out of friendship or his own vendetta against the village. Also, the elders of Konoha like Danzo could be important characters as they might be the ones behind Naruto's banishment.
The village elders are often depicted as the ones involved in Naruto's betrayal. They might see him as a threat to their power or the stability of the village. Also, some fanfictions might involve Danzo. He has always been a bit of a shadowy figure in the Naruto series, and his underhanded ways could easily be written into a plot where he is behind Naruto's false accusations and subsequent banishment.
The village elders are very likely to be involved. They often have a say in the big decisions in Konoha. They might be the ones who decide that Naruto must return for the safety or the benefit of the village. Tsunade could also be a part of it. If she's still in charge, she might be in a difficult position of having to order Naruto back or deal with the consequences of his forced return.
Obviously Naruto himself would be the central character. His friends like Sasuke and Sakura would also be involved. Iruka - sensei would play an important role as Naruto's teacher at the academy again. And characters like Kakashi might also make an appearance, perhaps to give Naruto some special training or advice based on his 'second chance' at the academy.
Definitely Iruka. He has seen Naruto grow up and has always supported him. Then there's Shikamaru. He's smart and he can see Naruto's value. He might support Naruto even if it goes against the village's decision at first. And of course, Kakashi. He has mentored Naruto and knows his potential, so he could be in Naruto's corner in these fanfictions.
Iruka and Mizuki are also possible characters for role reversal in fanfiction. Iruka could be the one with some hidden, not - so - good motives, while Mizuki could be the kind - hearted teacher figure. This would turn the early Naruto story on its head, as Iruka was Naruto's first positive influence in the original series. The new dynamic between Naruto and these two reversed characters would open up a whole new set of story possibilities.
Obviously Naruto himself. Then his parents, Minato and Kushina. His wife Hinata and their children would also be part of it. Jiraiya could also be involved as he was like a father figure to Naruto. And maybe some of the remaining Uzumaki clan members if they are still alive in the fanfiction. Also, characters like Iruka, who was an important person in Naruto's early life, could be there to witness the family reunion.
Naruto himself is very likely to be involved. He's the main character of his series and his unique abilities like the Rasengan and shadow clones would make for great interactions. Sasuke is also a top candidate. His Sharingan and his dark past could create interesting storylines when combined with hero concepts. Sakura, with her medical ninjutsu and strength, could also be involved, perhaps teaming up with a hero who has a similar healing - based power.
Obviously, Naruto himself is central. His family like Hinata and Boruto would be very likely to be involved. Sasuke is also a key character as Naruto's friend and ally. Kakashi, being Naruto's former teacher, could also play a role. Shikamaru, as Naruto's advisor, would be important in any political or strategic situations. And then there are the other members of the Konoha 11, like Sakura who could be involved in medical support or combat situations if needed.