Identity is a theme that comes up a lot too. Spider - Man is used to being a solo hero in his own neighborhood, and suddenly he's part of this big, global team. He has to figure out how to maintain his own identity while also being a part of the Avengers. And the Avengers have to learn to trust this masked hero with their secrets and operations.
One idea could be that during a mission crossover, Spider - Man gets injured while trying to protect a civilian from an unexpected attack by a powerful enemy. Maybe he takes a hit meant for an Avenger and his suit's technology malfunctions, leaving him vulnerable.
One interesting storyline could be Spider - Man teaming up with the Avengers to fight a new super - villain that's a combination of different powers they've faced before. For example, a villain with the strength of the Hulk and the mind - control abilities of Loki.
One great Spider - Man Avengers crossover fanfic is 'The Webs of the Multiverse'. It has an amazing plot where Spider - Man from different universes teams up with the Avengers to fight a powerful, multiversal threat. The character interactions are really well - written, especially the banter between Spider - Man and Iron Man.
The Avengers would be very concerned. Captain America would immediately take charge of the situation, trying to keep everyone calm while they assess Spider - Man's injuries. Iron Man would start scanning for the best way to treat him, using his high - tech equipment. Thor might offer some of his Asgardian knowledge of healing, if there was any. Black Widow and Hawkeye would be on guard, making sure there were no further threats while the team focused on Spider - Man.
In many Avengers fanfics, Spider - Man's sacrifice can be a very powerful plot point. It often shows his selfless nature. He might sacrifice himself to save his fellow Avengers or the world from a great threat. This kind of sacrifice also adds depth to his character as it shows his growth from a young hero to one who is willing to give everything for the greater good.
Iron Man is a great character to pair with Spider - Man. Tony Stark can act as a mentor to Peter Parker, providing him with new and advanced tech for his suit. They also have a fun dynamic, with Stark's sarcasm and Spider - Man's youthful exuberance.
Spider - Man could use his agility and web - slinging skills to escape. He could swing between buildings, making it difficult for the Avengers to follow him. His small size compared to some of the Avengers also gives him an advantage in hiding in tight spaces.
Spider-Man has definitely been in the Avengers in the comics. His presence has added a fresh dynamic and his powers and wit have been valuable assets to the group.