There could be a redemption arc in the fanfiction. Spider - Man might work hard to prove himself and clear his name. He could start by taking on smaller threats and gradually build his reputation back up. This might involve him saving the day in a very public way, which catches the attention of the Avengers again. Eventually, he could be reinstated into the team, but with a new - found respect for the importance of trust and loyalty within the group.
Another possibility is that in the fanfiction, Spider - Man's identity was revealed in a way that put the entire Avengers team at risk. The Avengers might then decide to distance themselves from him to protect their own secrecy and safety. This could involve kicking him out of the group to avoid any further potential threats associated with his exposed identity.
Tony could become a bit of a rogue figure. Maybe he starts to work against the Avengers at first out of anger and a sense of betrayal. This could lead to some really interesting confrontations between him and his former teammates in the fanfiction.
On the positive side, Spider - Man would have access to a whole new level of technology and training. He could learn from the likes of Captain America and Thor. However, he might also face some internal conflict within the team. The Avengers have different personalities and ideologies, and he might struggle to fit in at first. For example, he's used to being a solo hero in his neighborhood, and now he has to work with a large group of powerful individuals.
In some fanfictions, Tony might be kicked out of the Avengers because of a conflict in leadership styles. Maybe his high - tech and sometimes risky solutions don't sit well with other members who prefer more traditional or cautious approaches. For example, if a mission goes wrong due to one of his untested inventions, the team could lose faith in his decision - making abilities.
He could be seriously injured. The Avengers are a powerful group, and their combined attack would be hard for Spider - Man to withstand. He might end up with broken bones or other serious physical injuries.
Well, it could also happen that Peter's Spider - Man suit technology gives him away. Maybe the Avengers have some advanced tech - sensing equipment, and when Peter is around in his suit, it gives off some unique signals that the Avengers pick up on. So, they start to look into it and eventually figure out that Peter is Spider - Man.
The experiment could also make him an outcast. If the changes are too extreme, his friends and the public might be afraid of him. He would have to deal with the loneliness and the struggle to prove that he is still the same Spider Man at heart, just with some new abilities or features.
One idea could be that the Avengers are initially shocked but then become very protective of Spider - Man. They might start to train him more carefully, like Tony Stark making sure his suit has extra safety features. Another could be that some of the Avengers, like Captain America, take on a mentor role, teaching him about responsibility and heroism in a more age - appropriate way.
He could become more withdrawn. Losing Aunt May, who was like a mother to him, would be a huge blow. He might isolate himself from his friends and even from his crime - fighting duties for a while as he deals with his grief.
The Avengers could find out who Spider-Man is in fanfiction by a trusted insider accidentally spilling the beans. Or perhaps a villain uses this knowledge to manipulate the situation and forces the truth to come out.