Ned could be the main character in an alternate ending. He could find a way to hack into the Vulture's technology and disable his weapons. For example, while Spider - Man is busy in the physical fight, Ned uses his tech - savvy skills to disrupt the Vulture's flight systems, giving Spider - Man an edge in the battle.
Aunt May could be the main character in a different way. What if she somehow got involved in the fight? Maybe she discovers Peter's identity right in the middle of the chaos. Instead of freaking out, she uses her medical knowledge to help some of the injured civilians, and her calm presence also gives Peter the motivation he needs to finally defeat the Vulture.
One possible plot could be that instead of Peter Parker managing to defeat the Vulture on his own, he gets some unexpected help from an ordinary citizen. This citizen, inspired by Spider - Man's courage, steps in at a crucial moment, distracting the Vulture long enough for Peter to land a final blow. It would show that Spider - Man not only inspires fear in villains but also courage in the common people.
A new character could be a tech - savvy girl who discovers Peter's identity and offers to be his 'Q' of sorts. She helps him upgrade his suit and gives him new gadgets to fight crime with.
It could be a mad scientist who creates mutated creatures to cause chaos in the city.
Captain America could also be an interesting crossover. They have different outlooks - Spider - Man is young and still learning, while Captain America has strong moral values. A story where they team up to stop a group of super - villains who are trying to undermine the city. Captain America could teach Spider - Man about leadership and making tough decisions.
MJ and Ned could also be part of this. If Peter's journey in an alternate ending takes him to other universes, they might be left behind at first. But then they could find a way to also get involved in multi - universe adventures, either by finding a way to travel to other universes themselves or by helping Peter from their own universe in some unexpected ways.
One new character could be an alien who crash - lands near New York. This alien is initially seen as a threat, but Peter discovers that the alien is actually on the run from a more powerful and evil alien race. Peter decides to help the alien, and in the process, he learns some new combat techniques from the alien's unique physiology. This could add a whole new dimension to the Spider - Man Homecoming sequel fanfiction.
Maybe Peter Parker faces a new and more powerful villain. For example, a super - intelligent criminal who can hack into any technology in New York. Peter has to use his wits and new skills he's developed since the first movie to stop him.
In fanfiction, perhaps Spider - Man discovers a hidden part of his powers. He might also have to deal with some personal issues at school while fighting bad guys. For example, he could be struggling with a difficult exam while also trying to stop a heist by a group of tech - savvy thieves. And his relationship with his friends could be put to the test as he tries to keep his identity secret from them.
In a Spider - Man Homecoming Flash fanfiction, Flash could start as the typical bully. But one day, while being chased by some street thugs, Spider - Man saves him. Flash realizes that there's more to the world than just being popular at school. He begins to secretly admire Spider - Man and tries to change his ways. He starts to stand up for the weaker students, inspired by the heroism he witnessed. Eventually, he might even become an unexpected ally to Spider - Man, using his knowledge of the school and its students to help Spider - Man keep an eye on any potential threats.