A possible plot idea is that Batman discovers a way to bring back some of the fallen heroes from different Batverses. This could lead to a story where he has to convince these heroes to fight alongside him again, while also dealing with the consequences of messing with the fabric of the Batverse. He could face opposition from some characters who believe this will disrupt the balance of the multiverse.
Perhaps in the fanfiction, Batman gets trapped in a Batverse where Gotham is a utopia. He has to figure out how this came to be and if there's a dark secret behind it. He might also find that the villains in this version of Gotham are not what they seem. They could be hiding their true nature while pretending to be reformed, and Batman has to expose them before they carry out a grand scheme.
The Batman Who Laughs could also serve as the main antagonist. He represents a twisted version of Batman, and his goal could be to infect all the Batverses with his madness. His knowledge of Batman's tactics and his own insanity would pose a huge challenge for the normal Batman as he tries to stop him from spreading chaos.
Perhaps they could start off as rivals in the fanfiction. Batman from the present is skeptical of Batman Beyond's more high - tech approach. But as the story progresses, they learn from each other and become a great team. For example, Batman could teach Batman Beyond some of his old - school detective skills, while Batman Beyond shows Batman new ways to use technology in combat and surveillance.
One idea could be exploring what if Bruce Wayne's identity as Batman was exposed accidentally by a new high - tech surveillance system in Gotham. Another could be a story where Batman has to take on a new identity temporarily to infiltrate a secret criminal organization that has been studying his every move as Batman.
A plot could involve a time - travel scenario where Batman and Supergirl are sent back in time to prevent a major event that would change the future of both their worlds. They would have to work together, using their different skills and knowledge of their respective eras.
One idea could be exploring the relationship between Batman and Robin in a more emotional depth. Maybe Robin is going through a tough time at school and Batman has to balance being a mentor and a crime - fighter. Another could be a time - travel plot where the Bat - family gets sent to different eras in Gotham's history and has to adapt and still fight crime.
One idea could be that Batman and Robocop team up to take on a powerful criminal organization that is using high - tech weaponry. They would combine Batman's stealth and detective skills with Robocop's firepower and law enforcement programming.
One idea could be Batman using his detective skills to uncover a hidden threat that the Avengers initially overlook. For example, he might notice some small, seemingly insignificant details during a battle scene that lead him to a much larger conspiracy.
One idea could be exploring the psychological state of Batman during Knightfall more in - depth. Maybe focus on his nightmares and how they affect his decisions in the story. Another could be a what - if scenario where a different character takes on the role of protecting Gotham during Knightfall, like Oracle guiding a team of young vigilantes.
One idea could be exploring Batman's internal struggle in the Injustice universe more deeply. Maybe he has a nightmare where he becomes like the tyrannical Superman, and this makes him question his own actions and methods even more.
One idea could be a story where Nightwing has to take over Batman's duties temporarily in Gotham. He faces a new villain who is specifically targeting Batman's absence and Nightwing has to prove himself not just as a replacement, but as a hero in his own right.