One idea could be that the stalker is a villain who wants to expose All Might's secrets to undermine his heroic image. Another could be a misguided fan who thinks they are protecting All Might but their actions are actually causing trouble. Maybe the stalker has some sort of connection to All Might's past that they are trying to uncover.
A really engaging plot might be that the stalker is someone who was wronged by a decision All Might made in the past. They are now stalking him to get revenge in a very elaborate and sneaky way. They could be setting up false situations to make All Might look bad in the public eye. They might also be trying to get close to his proteges like Midoriya to use them against All Might.
A character who could be the stalker is Gentle Criminal. He has that sort of flamboyant and devious nature that could lead him to stalk All Might out of some strange admiration or to prove himself as a worthy 'opponent'.
One idea could be that the villains release a powerful virus that turns most of the population into mindless zombies. The heroes have to not only fight the villains but also deal with the zombie horde. Another could be an apocalyptic event that wipes out most of the world's quirks, and the remaining heroes and villains must adapt to this new powerless world.
Maybe in the 'bnha graduation fanfic', there's a competition among the students as part of the graduation. The winner gets a special internship or a chance to work with a top hero. This could lead to intense rivalries and unexpected alliances.
One interesting plotline could be her struggle to live up to her father's legacy. Since All Might is such a great hero, she might constantly feel the pressure to be as good as him. Another could be her dealing with the attention she gets because of her relation to All Might, whether it's positive or negative attention from the public or other heroes.
A good plot could be a villain being sent to an alternate dimension where they experience a life without quirks. They see how normal people live and cooperate, and this makes them realize that their use of power for evil was wrong. When they return to their own world, they are determined to reform.
One idea could be focusing on the children of the main BNHA characters dealing with new villains who have unique powers. They could struggle to live up to their parents' legacies while also finding their own identities.
One idea could be a hero with an illusion quirk who uses it to create false distractions during battles. For example, making the villains see an army of heroes when there are really only a few, causing them to waste their attacks and energy.
One idea could be exploring how the characters' relationships change. For example, if Deku was a girl, how would her dynamic with Bakugo be different? Maybe Bakugo would be more protective in a different way. Another plot could focus on how the female versions of the male heroes deal with the challenges in the hero society, like discrimination that might be specific to female heroes. Also, a plot could revolve around a genderbend All Might and how she inspires the new generation of heroes.
Well, a plot could revolve around the Sith Stalker being sent to infiltrate a Jedi stronghold. They have to disguise themselves as a Jedi initiate. During this time, they start to form unexpected friendships with some of the Jedi. This causes a conflict within them as they are supposed to be loyal to the Sith. They must then decide whether to complete their mission or betray the Sith for their newfound friends.
A plot could revolve around a new transfer student who brings the game to UA. As the students play, it causes some friendly rivalries and new friendships to form. For instance, when a card reads 'The most embarrassing hero costume flaw', the students' answers could lead to some good - natured teasing and bonding. This could also be a way to explore different characters' sense of humor.