Well, in some fanfictions, Tony and Steve's relationship could be completely different during the reverse time heist. Maybe they start to understand each other better as they work together in the past. They could see the reasons behind each other's actions in a new light.
Maybe in the fanfiction, the reverse time heist goes wrong in a different way. Instead of getting the stones, they end up changing key events in the past that have unforeseen consequences in the present. For example, they prevent the birth of one of their own members, and then have to figure out how to fix it while still dealing with Thanos. It would be a complex and interesting storyline.
When it comes to Steve Rogers, the time heist could be used to further explore his longing for the past. In the movie, he goes back to be with Peggy. But in the fanfic, it could show his internal struggle about leaving his present friends. It could also show his joy and sadness as he revisits key moments in his past, and how he ultimately makes the decision to stay or go back in time more comprehensively.
One idea could be exploring the different Avengers' reactions in more detail as they go back in time. For example, Tony Stark might have some internal conflicts about seeing his younger self and the technology of the past. Another plot idea could be the unexpected encounters with characters during the time heist that weren't in the movie. Maybe they run into some alternate versions of villains that change the course of the heist.
Well, some relationships might become stronger. For example, Thor and Rocket might bond more over their shared experiences in Endgame. They could start to rely on each other even more in future battles.
It could strengthen them. For example, Black Widow and Hawkeye might have a closer bond as they both see the enormity of the situation in the trailer. They might rely on each other more, knowing that they need to be there for one another in the upcoming battle.
The characters are often filled with grief. They see their friends and comrades die in Endgame, and this can bring out deep sadness. For example, Thor might be even more broken - hearted seeing his brother Loki's death again. Captain America could feel a sense of guilt, thinking he could have done more to prevent some of the deaths.
Loki is another favorite. His mischievous nature means that he could cause all sorts of chaos during time travel. He might try to take advantage of the time - jumping to create his own power base in different timelines or even try to outwit Thanos in ways that the other Avengers can't.
Thor is very popular in post - Avengers Endgame fanfiction. His journey of self - discovery after Endgame, from being out of shape and depressed to finding a new path, is a rich area for fanfic writers. Wanda Maximoff is also a favorite. Her power and the emotional turmoil she went through in Endgame, especially with Vision's death, are often delved into. Additionally, Clint Barton, with his complex past as Ronin and his family life, is a character that many fanfic authors like to focus on in the post - Endgame world.
Some relationships might become stronger. If they read fanfiction that shows deep friendships between them, they could be more aware of their bond. For example, if there are stories about Iron Man and Captain America's friendship overcoming differences, they might be more likely to work together better.
They could become closer. Sharing a laugh over some of the wilder fanfiction plots would create a new bond. For example, if there was a really out - there story about Hawkeye and Black Widow having secret superpowers, they could joke about it together.