In many aspects, 'Across the Spider-Verse' adheres to the comic book canon. However, there might be some creative liberties taken to make the story more cinematic and engaging for the audience while still respecting the core elements of the comics.
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.
One great 'Across the Spider - Verse Fanfic' is 'Spider - Verse Bonds'. It focuses on the relationships between different Spider - People. It shows how they interact, support each other, and grow together in this multiverse. It has really engaging character development.