Maybe in this fanfiction, the Star Wars Force is related to the Quirks in My Hero Academia. The characters have to figure out how to combine the two powers. Some of the Star Wars characters could be interested in learning about Quirks, and vice versa. Like Luke Skywalker might be intrigued by All Might's strength and try to understand how it works in relation to the Force.
Deku could also be very fascinating. His journey from a quirkless boy to a powerful hero could be paralleled in the Star Wars universe. He could start as an unknown in the galaxy and gradually gain recognition for his unique abilities (his Quirks). He might even have to learn about the Force while still relying on his Quirks, which would create an interesting internal struggle.
How about a fanfiction where the villains and heroes have to team up? There could be a greater threat, like an alien invasion or a powerful quirk - user who is out to destroy the entire world. The heroes and villains realize that they can't defeat this threat alone, so they put aside their differences. This would lead to some really interesting character interactions, like Bakugo having to work with Shigaraki and both of them learning to respect each other's skills despite their opposing natures.
Well, a really interesting plot could be that the Force in Star Wars is actually a form of quirk that has evolved differently in a galaxy far, far away. The characters from My Hero Academia, when they cross over, have to learn to use the Force as if it were their quirks. For example, Bakugo's explosive quirk could be related to some dark side Force power. He would then have to struggle with the temptation of the dark side, just like Anakin Skywalker did. And perhaps the Jedi Council would be intrigued by the unique nature of these 'quirky' visitors.
An interesting plot could involve an anti - hero who has a hidden agenda that is not entirely evil but also not in line with the traditional hero goals. Maybe they are trying to expose a corrupt part of the hero society from within. They could form alliances with some villains who also have a vendetta against the corrupt elements. This would create a complex web of relationships and moral dilemmas.
One plot idea could be a villain who is secretly a double agent, working for the heroes all along. They infiltrate the villain group and gather information. Another idea is a hero who loses their quirk and has to rely on their wits and combat skills alone, like Batman in the DC universe. And a villain - hero team - up to face a greater threat that neither can handle alone.
Maybe a plot where a group of Warhammer heroes are sent to the Hero Academia world to stop a chaos invasion that is starting to seep into that realm. They have to work with the local heroes, sharing their knowledge of dark magic and ancient weapons to combat the new threat. This would involve a lot of cultural clashes and learning experiences between the two groups.
One possible plot could be that a powerful villain manages to release a virus that turns most of the population into mindless, powerful mutants. The remaining heroes, including the students of UA, have to not only fight these mutants but also find a cure. Deku could be leading the group, trying to figure out how to use his new powers in this chaotic situation.
A plot could revolve around Wolverine being sent to the My Hero Academia world to hunt down a mutant - like being that has escaped into this universe. However, he quickly realizes that the world has its own set of rules and heroes. He teams up with Midoriya and the others to find this being. Along the way, he teaches them about survival and the harsher side of combat, which is different from what they learn at UA. And in the end, they all learn from each other and Wolverine has a newfound respect for the young heroes.
An interesting plot could involve an OC who is initially thought to be quirkless but discovers a latent quirk later on. This OC could then struggle to catch up with the others in terms of training and development. Or, an OC with a shapeshifting quirk could be used in a plot where they have to infiltrate a villain's lair by taking on the form of one of the villains' minions. They would have to be careful not to be discovered and also gather intelligence along the way.
One possible plot could be Sans using his teleportation ability (from his original game) in the My Hero Academia world to outwit villains during a big battle. For example, he could suddenly appear behind a villain like Stain and disarm him before he even realizes what's happening.