Well, a cool plot could involve Spider - Man's identity being revealed to the public and the Avengers having to protect him from various villains who see this as an opportunity to take him out. Or perhaps a situation where an old enemy of the Avengers teams up with one of Spider - Man's foes, forcing the two groups to work together more closely than ever. Spider - Man could also introduce some new tech or fighting styles to the Avengers during their joint adventures.
Here's an interesting plot. The Avengers are dealing with a powerful cosmic threat that is causing chaos across the universe. Spider - Man, while swinging around New York, stumbles upon a strange artifact that has a connection to this threat. He then contacts the Avengers, and they realize that his discovery might be the key to stopping the menace. Along the way, Spider - Man has to prove himself to some of the more skeptical Avengers members, like Iron Man, who initially doubts his ability to handle such a large - scale threat. As they work together, they learn from each other's strengths and weaknesses and ultimately save the day.
A plot could involve Spiderman accidentally getting caught in an Avengers - level battle right in his neighborhood. He then has to prove himself to the Avengers while also protecting his home and friends. Maybe he discovers a connection between the villain in the battle and the local crime in his area that he's been trying to stop in 'Homecoming'.
One idea could be that Spiderman discovers a new threat in his neighborhood which turns out to be linked to a much larger plot involving the Avengers. So he has to convince the Avengers to take him seriously and work together to stop it.
One plot idea could be that the Avengers discover Spiderman's identity during a mission when his mask gets damaged. Then they have to protect his secret from villains who are also after it.
How about a crossover with the Hulk? Spiderman might be on a mission in a city when the Hulk goes on a rampage. Instead of fighting the Hulk directly, Spiderman has to figure out a way to calm him down or lead him away from the populated areas. Along the way, they could encounter some other villains who are trying to take advantage of the situation, and then they end up teaming up to defeat the villains.
One idea could be that they team up to take on a new super - villain who has the ability to manipulate time. Deadpool's unpredictability and Spiderman's quick thinking would make for an exciting combination in this scenario.
One interesting plot could be Spiderman getting caught in the middle of an Avengers' internal conflict. Maybe there's a disagreement among the Avengers about how to handle a new threat, and Spiderman has to use his unique perspective and abilities to try and bridge the gap. For example, Iron Man might want to use high - tech solutions that could endanger civilians, while Captain America is more focused on protecting the people first. Spiderman, being a street - level hero, can relate to both sides and tries to find a compromise.
One idea could be a Spiderman and Iron Man crossover. Picture Spiderman getting some high - tech upgrades from Stark. Another is a crossover with the X - Men. Spiderman could interact with mutants and learn new ways to use his powers. Maybe he teams up with Wolverine for a street - level mission.
A plot could involve the Avengers trying to understand the Flash's powers. Tony Stark might be especially intrigued and try to create technology to mimic the speed force. Meanwhile, the Flash could be in awe of the Avengers' different abilities and learn new ways to use his speed from them. For example, he could learn combat strategies from Captain America or how to better control his powers from Doctor Strange. And then they all have to face a threat that only their combined powers can defeat, like a cosmic entity that is draining the life force of both their universes.
One idea could be that the Eternals' powers are needed to defeat a new, extremely powerful villain that the Avengers alone can't handle. For example, a cosmic entity that can manipulate time and space. The Eternals' long - lived knowledge and unique abilities would be crucial in formulating a battle plan.
Well, perhaps in the fanfiction, there could be a cultural exchange of sorts. The Eternals could introduce the Avengers to their long - lived and different ways of life. This might lead to some interesting character development, like Thor learning new forms of combat from an Eternal warrior. Also, the discovery of a hidden connection between the two groups, such as a shared ancestry in some ancient, forgotten time, could be a great plot point.