One idea could be that different versions of Spiderman from across the multiverse team up to fight a common enemy that can travel between dimensions and is threatening all their worlds. For example, a powerful symbiote - like creature that has the ability to absorb the powers of each Spiderman it defeats.
For a 'Spiderman into the Spider - Verse fanfic', you could have a plot where the Spot, who has been working on a new super - weapon in secret, manages to open portals to multiple universes all at once and unleashes a horde of minor villains from each. The Spider - People from different universes have to band together not only to fight these villains but also to close the portals. There could be a sub - plot about a relationship developing between two Spider - People from very different universes, like one from a steampunk world and another from a world of magic. This relationship could add an interesting emotional layer to the story as they struggle to save the multiverse.
One idea could be exploring a different Spider - Person's origin story within the multiverse. For example, a Spider - Person from a world where spiders are sentient and work together with the human Spider - Person. Another could be a story where all the Spider - People have to team up against a villain who can manipulate time across the multiverse, causing chaos and disrupting the fabric of each Spider - Verse.
One interesting plot idea could be a story where Miles Morales teams up with a version of Spider - Man from an alternate dimension who has the power to control time. They have to stop a villain who is using time - based technology to rewrite history and make himself the ultimate ruler.
One idea could be exploring the different Spider - People's home universes in more detail. For example, showing what Miles Morales' daily life in his universe was like before becoming Spider - Man. Another could be a team - up between Miles and an older, more experienced Spider - Person from a different universe to face a new and powerful villain.
For an Into the Spider - Verse crossover fanfiction, how about a crossover with the Teenage Mutant Ninja Turtles? They could fight together in the sewers of New York against a common enemy like the Foot Clan. Another possibility is a crossover with Hellboy. Spider - Man and Hellboy could combine their powers to defeat a demon that's causing chaos in the city. And a crossover with the Power Rangers would be interesting too. The Rangers' teamwork and their zords could be combined with Spider - Man's agility and web - slinging abilities to take on a huge monster.
Maybe Naruto finds himself in a dimension where all the Spider - Verse characters are facing a threat that only his unique jutsu can solve. He has to work with Miles Morales and others to understand their powers and how his ninja techniques can complement them. It could lead to some really cool fight scenes and character interactions.
Another idea is a time - travel fanfiction. Spider - Man could be sent back in time to when his Uncle Ben was still alive. He would have the chance to prevent his uncle's death, but he'd also have to deal with the consequences of changing the timeline, like how it might affect his own development as a hero.
A cool plot could involve a young Peter Parker from a universe where he got his powers much later in life. He ends up in the main Spider - Verse and has to learn quickly from Miles and the other Spider - People. They could all work together to stop a symbiote - like entity that is infecting different versions of Spider - Heroes. It would be interesting to see how this inexperienced Peter copes with the situation and how his different perspective might help solve the problem.
You could write a fanfiction about the origin of the Spider - Verse itself. Maybe it was created by a super - intelligent spider from a far - off dimension who wanted to bring together all the possible versions of Spider - People. Or perhaps a story where a new Spider - Person emerges in a dimension that has never had one before and how they adapt to their new powers and the knowledge of the Spider - Verse. Also, a story about the villains teaming up across the dimensions to take on all the Spider - People at once would be cool.
One idea could be exploring what would happen if Miles Morales had to team up with an alternate version of himself from a dimension where he didn't become Spider - Man. Maybe in that dimension, he became a villain instead. Another idea is to focus on Gwen Stacy's story more, like her adjusting to life in a new dimension where she has different relationships with the other Spider - People. You could also write about a new villain that emerges specifically targeting the multiverse of Spider - People and how they all come together to stop it.