The Bnha universe's reaction would be mixed. Those who are into complex stories, like Todoroki, might study the relationships in Hamilton fanfiction. But others, like Mineta, might not be interested at all because it doesn't have much to do with his usual interests. Overall, it would depend on the individual characters' personalities and interests.
Hamilton would probably have a complex reaction. He was a man who valued his reputation and the truth. Fanfiction often bends the truth for the sake of creativity. So he could be initially put off, but then as he reads more, he might see the charm in the creative interpretations of his life.
Some characters might laugh. They would see the humorous side of how fans have twisted and turned their stories. It could be like seeing a new, comical version of their own lives as depicted in the musical.
They might be really confused at first. The world of 'Bnha' is so different from the historical and musical context of 'Hamilton'. But some characters could get inspired by the themes of ambition and fighting for what you believe in that are in Hamilton fanfiction.
For heroic - centric fanfictions, they would likely be disdainful. Since they oppose heroes, seeing stories that glorify heroes would annoy them. They might scoff at the idealized versions of heroes in those fanfictions.
Some would be inspired. Characters like All Might might see Peter Parker's journey as similar to his own in some ways. Both are trying to do good in a world full of challenges. All Might could appreciate Peter's determination to protect his city despite having a normal life outside of being a hero.
Well, consider Hamilton's son. He would be scared and confused, not fully understanding what's happening to his father. He might try to be brave and do little things to make Hamilton feel better, like drawing pictures for him. Hamilton's friends in the military, like Laurens, if he were still alive in this fanfiction, would be ready to defend Hamilton from any potential threats during his illness. They would be on high alert because they know Hamilton has enemies. And the ordinary people who have been inspired by Hamilton's ideas would be praying for his recovery and sending well - wishes, which would add to the sense of Hamilton's importance in the community.
Sakura would probably be both scared and fascinated. She might initially be frightened by the dinosaurs but then use her medical ninja skills to help any injured people. Sasuke would be more aloof. He'd likely see the dinosaurs as just another challenge. He might study their behavior to find weaknesses and use his sharingan if any of the dinosaurs pose a real threat.
The more philosophical fanfiction would intrigue the Jedi Masters. Yoda, for instance, would probably nod his head and say 'Much to think about, there is in these words.' They would see it as an opportunity to further explore the concepts of the Force, good and evil, and the nature of the Star Wars universe. However, the average stormtrooper might not understand it at all and just shrug it off as some strange mumbo - jumbo.
The gamer reincarnation concept fits in by adding a new layer of complexity. It allows for different power dynamics as the reincarnated gamer often has a different way of approaching their quirk or abilities compared to native BNHA characters. For example, they might see their quirk as a game mechanic, leveling it up and strategizing in ways that are foreign to the regular BNHA characters.
I think Hamilton would be rather curious. Fanfiction can offer different perspectives on his life that he might not have considered. He would probably be most interested in those that explored his intellectual side, his writing, and his ideas for the new nation. He might be a bit taken aback by some of the more fictionalized elements that deviated too much from the historical facts, but at the same time, he might recognize the creativity behind them. He could also be interested in how the fanfiction was received by the public, as he was always aware of his public image during his life.