One idea could be a story where Rachel survives and she and Bruce try to have a normal relationship while still dealing with the crime in Gotham. Maybe she becomes more involved in his crime - fighting efforts in a non - violent way, like helping with the rehabilitation of criminals he catches.
Perhaps a fanfiction could focus on the backstory of Harvey Dent before he became Two - Face. It could show his early days as a prosecutor and how his idealism gradually got corrupted, which would add more depth to his character in the Dark Knight universe.
You could also say their relationship is one of contrasts. Bruce is dark, brooding, and lives in the shadows as Batman, while Rachel is a symbol of light, justice in the legal sense. She represents the hope that Gotham can be saved through the law, while he takes a more direct and often violent approach. Their love bridges these two different worlds, at least for a while.
One idea could be exploring what if Batman had a different sidekick in the 'the dark knight rises' fanfiction. Maybe a young girl with special tech skills who helps him in new ways.
One interesting plot idea could be exploring Bane's backstory more in - depth. Maybe delving into his early days in the prison and how he became the menacing figure we see in the movie. Another could be a different take on his relationship with Talia al Ghul, like if there were hidden motives or unspoken feelings between them.
One plot idea could be that Jane somehow gets caught in the middle of the battle between Batman and the Joker. Maybe she starts off as an ordinary citizen who witnesses a crime related to the Joker's chaos. As she gets involved, she discovers that the Joker has a strange fascination with her, seeing her as a new kind of plaything. This could lead to a series of tense encounters where Batman tries to protect her from the Joker's unpredictable and dangerous schemes.
Perhaps a fanfiction could explore what would happen if the Dark Knight was suddenly the only one with his memories intact in the Justice League due to some sort of mind - wiping event. He then has to slowly regain the trust of his teammates while also trying to figure out what caused the memory loss and stop a new threat that is emerging, all while operating in the shadows as he usually does.
A plot idea might be that a long - lost relative of Ra's al Ghul comes to Gotham seeking revenge for his death. This new character could bring in some of the League of Shadows' old ways but also modern twists. Also, we could see the return of Catwoman in a more complex role, perhaps having to choose between her own interests and the good of Gotham.
One plot idea could be Harley trying to break free from the Joker's control in a more psychological way. Maybe she starts having dreams that show her a different life without him, and she begins to question their relationship while still being in love with him. Another idea is a story where the Joker and Harley team up with other villains from the Dark Knight universe against a common enemy. For example, they could join forces with Bane to take over Gotham, but there are internal power struggles within their alliance.
One possible plot could be that Bruce's goddaughter discovers his secret identity as Batman. She might initially be shocked but then decides to help him in his fight against crime. Maybe she uses her own unique skills, like being a tech - savvy hacker, to assist Batman in gathering information on his enemies.
One interesting plotline could be Bruce and Selina teaming up to take on a new criminal threat in Gotham that the police are unable to handle. They start off as reluctant allies but gradually grow closer as they face danger together.