The mom could be shocked at first but then gently explain to the son that it's a private and natural but not something to be begged for. For instance, she might say that farts are a normal body function but not something we should play around with in this way. She could also use this as an opportunity to teach the son about good manners.
In many BNHA fanfictions where Izuku meets All Might early, it often changes the entire trajectory of Izuku's development. For example, he might gain confidence much sooner. Early meetings can also lead to a more in - depth mentorship that might deviate from the original storyline. This could result in Izuku getting special training earlier and potentially unlocking his Quirk in a different way.
One consequence could be a faster growth in Izuku's power. With All Might's early guidance, Izuku may master his Quirk more quickly. Another is that his relationships with other characters might change. For example, Bakugo could become more jealous or, on the contrary, might be inspired to work harder.
Villains who want to use her as a bargaining chip against All Might could be main antagonists. They might think that by capturing her, they can force All Might to do their bidding.
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 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 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.
On the other hand, the son might try to adapt in a way to please his mom at first. But as time goes on, he will likely start to feel a great internal conflict. He might start to secretly explore his true identity while still pretending to be a girl for his mom. This could lead to a lot of secrecy and emotional turmoil within him as he tries to balance his true self and his mom's expectations.
The boy might be confused at first. He may not understand why he is being dressed differently from other boys he sees. For example, if he goes to school in a dress, his classmates might stare or make comments, which could make him feel self - conscious.
The son might initially be very confused. He's a boy and being forced into a 'daughter' role is something completely alien to him. He may resist, not understanding why his mom wants him to do this.