A possible plot idea is that during the reverse time heist, there are glitches in the time travel that cause the Avengers to swap abilities or powers temporarily. This could lead to some really comical and also challenging situations. Also, what if there was a love interest for one of the Avengers in the past that they had forgotten about, and it resurfaces during the time heist and causes some drama within the group.
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.
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.
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.
Well, in some fanfictions, the time travel might go wrong in a way that it starts to merge different timelines. So the Avengers not only have to deal with Thanos but also with the chaos of colliding timelines. For example, characters from different points in time start interacting in strange ways, like an older version of Iron Man meeting his younger self. This can lead to a lot of interesting character development and conflict resolution.
A really cool plot idea could be that the Avengers are watching Endgame in a sort of 'alternate reality cinema' where the events in the movie start to bleed into their real world. So they have to stop the movie from fully playing out to prevent chaos in their own universe. This would involve a lot of action and strategic thinking as they try to stop things like Thanos from emerging from the screen while also trying to understand the significance of what they're seeing in the movie.
One idea could be a crossover with the Doctor Who universe. The Avengers could team up with the Doctor to fight a common enemy that threatens both their universes. Maybe Thanos somehow gets access to Time Lord technology and the combined forces have to figure out how to stop him from using it to rewrite all of reality.
Perhaps a fanfiction where the Infinity Stones in the Endgame have an unexpected effect on certain anime characters. These characters start to develop new abilities or forms that are a blend of their anime selves and the power of the Stones. This could lead to a whole new dynamic in the fight against Thanos, as the Avengers have to figure out how to work with these newly - empowered anime allies.
One idea could be an OC who has the power to time - travel in a unique way, not like the Avengers' method. They could accidentally disrupt the events of 'Endgame' further while trying to help. For example, they might create alternate timelines where different villains gain power. Another plot could involve an OC who is a long - lost relative of one of the Avengers. They show up during the final battle and use their hidden powers to turn the tide. And a third idea is an OC who is from a different dimension entirely and has knowledge of how to defeat Thanos more easily, but they have to convince the Avengers to trust them first.
One idea could be exploring Red Skull's redemption arc. Maybe in the fanfiction, he somehow manages to break free from his eternal punishment on Vormir and joins the Avengers in the final battle against Thanos. He could use his knowledge of the Soul Stone and the other Infinity Stones to help the Avengers turn the tide.
In some 'Avengers Endgame Fix It Fanfiction', there might be a concept of time travel without the glitches that occurred in the movie. Maybe they could have a more stable time - travel device which allows them to not only reverse the snap but also fix other events that led to Thanos' victory. This could involve changing things like Loki's escape with the Tesseract in a more beneficial way for the Avengers.