Another plot could revolve around the creation of a new school that combines the teachings of UA and Beacon. The students would have to learn to adapt to different fighting styles and powers. There could be a lot of drama and friendship building as they compete in new types of challenges.
Maybe there could be a quirk - semblance exchange. A character from My Hero Academia could temporarily gain a RWBY character's semblance and vice versa. This would lead to some really cool and unexpected battle combinations. Like Deku having Ruby's speed semblance for a while and using it in a creative way during a fight.
A great crossover idea is with the Dragon Ball series. The powerful Saiyans could interact with the My Hero Academia characters. Goku could train the students at UA to reach new levels of power. Also, a crossover with the Attack on Titan world would be intense. The heroes would have to deal with Titans in a whole new way and use their quirks in that battle - filled environment.
A great plot might be a training exchange. The heroes from My Hero Academia go to the DC universe to train with Superman and Batman. They learn different combat and strategic techniques. In return, they teach the DC heroes about quirks. This could lead to some really interesting character interactions. For instance, Bakugo might have some intense sparring sessions with Wonder Woman, and both would learn from each other.
Maybe there could be a plot where a villain from Overwatch steals some of the quirk - enhancing technology from My Hero Academia. This forces the heroes of both universes to work together to get it back. For example, Tracer and Deku could team up. Tracer's time - jumping ability and Deku's One For All would make for an exciting duo in the chase.
A cool plot could involve the sharing of techniques. Sasuke might teach Bakugo some of his sword skills, while Bakugo shows Sasuke how to better control his explosive power without overusing it. Also, the concept of the Ninja Academy in Naruto could be merged with UA High. Students from both could participate in a joint training session where they learn from each other's combat styles and strategies.
One plot idea could be that the heroes from My Hero Academia end up in the Soul Society of Bleach. They could learn about the different spiritual powers there and team up with the Soul Reapers to fight a common enemy, like a powerful Hollows that have somehow invaded both worlds. Another idea is that the Quirks from My Hero Academia start to manifest in the Bleach universe, causing chaos as people with Quirks are not the norm there. And perhaps Ichigo could visit UA Academy and learn about hero training, and even participate in some hero battles.
One idea could be a crossover with the Naruto universe. The characters from My Hero Academia could interact with Naruto characters. For example, Deku might learn some new fighting techniques from Naruto. Another idea is a crossover with the Harry Potter world. The students at U.A. could visit Hogwarts and experience magic, while the Hogwarts students could learn about quirks.
A cool My Hero Academia crossover fanfiction idea would be with the Avengers. The heroes from UA could team up with the Avengers to fight a common enemy. For example, a powerful villain who can absorb quirks and powers. It would be interesting to see how characters like All Might and Captain America interact, and how their leadership styles differ.
One idea could be that the Demon Slayers are brought into the world of My Hero Academia. Tanjiro could learn about quirks and try to figure out how to use his skills in this new environment. Maybe some of the demons also gain quirks which makes them even more dangerous.
One interesting idea could be a crossover with another popular superhero universe, like Marvel or DC. This could lead to epic battles between different types of heroes. Another idea might be a crossover within the My Hero Academia world itself, for example, different classes or generations of heroes teaming up in unexpected ways.
One idea could be that Naruto characters are transported to the My Hero Academia world. Naruto himself could be seen as having a very unique quirk, like his chakra manipulation could be considered a superpower. They could team up with the students of UA to fight against a common enemy, like a group of villains who are after the secrets of chakra. Another plot could involve the My Hero Academia characters traveling to the Naruto world and learning about ninjutsu and how it differs from their quirks.