One idea could be that Batman gets injured during a fight with a new super - villain. A young fan witnesses this and decides to step up and help in his own way. Maybe he uses his knowledge of technology to create something that aids Batman's recovery or gives him an edge in the next encounter.
Perhaps Batman is injured while saving the fan from a dangerous situation. The fan, feeling guilty, then embarks on a journey to find a rare herb or medicine that is said to have miraculous healing powers. Along the way, he meets various characters from the Batman universe who either help or hinder his quest.
A plot idea could be that Nightwing is injured while saving a group of hostages. Batman then has to deal with the criminals who were holding the hostages as well as take care of Nightwing. The story could explore Batman's feelings of guilt for not being there in time to prevent Nightwing's injury.
Perhaps Batman is injured in a trap set by the Joker. While he's injured, the other villains in Arkham Asylum sense his weakness and start planning a mass breakout. Batman has to use his wits and the help of Oracle to stop them from the confines of his Batcave, all while nursing his injuries.
In a fanfiction, Robin could be injured in a trap set by an old enemy of Batman. This enemy specifically targeted Robin to get back at Batman. Batman, upon finding Robin injured, is consumed with guilt and anger. He goes on a full - scale investigation to find the enemy. Meanwhile, Robin is in a critical condition and Alfred has to use all his medical knowledge to keep Robin alive. The story could focus on Batman's internal struggle between his need for revenge and his responsibility to Robin, and how he overcomes this to save both Robin and Gotham.
One plot idea could be that Connor gets injured during a mission. His friends then have to figure out how to get him to safety and repair him. Another could be that Connor is injured by a malfunction in his own system, and he has to struggle with the internal conflict while also dealing with the physical pain. Maybe he gets injured while protecting someone, and that person then feels a sense of guilt and tries to help him recover.
A plot idea could be that Batman is injured by a kryptonite - enhanced weapon during a fight against a Lex Luthor - controlled Superman in the Justice League. His injury makes the other members realize how vulnerable they are without Batman's strategic mind. So they have to find a way to heal him quickly while also preventing Luthor from causing more chaos.
In this fanfic, there could be a scenario where Batman is exposed to Kryptonian technology that gives him some Kryptonian - like abilities temporarily. A Kryptonian comes to Earth to study this anomaly. They start off as adversaries but as they learn more about each other, they find that they can work together to protect Earth from a greater threat that only their combined skills can defeat.
One plot idea could be that Cole Sprouse is filming on location and accidentally causes a minor injury to a fan who was too close to the set. He then feels extremely guilty and spends time with the fan in the hospital, getting to know them and realizing they have a lot in common. As a result, a beautiful friendship begins.
One plot idea could be that a fan gets injured while trying to get close to Harry Styles at a concert. Maybe she faints in the crowd and hits her head. Harry notices and stops the show to make sure she gets proper medical attention. Then the story could follow her recovery and Harry checking in on her, which leads to an unexpected friendship.
A plot idea could be that Poison Ivy creates a new type of plant - based virus in Arkham that only affects humans who are harming the environment. Batman has to find a way to stop the virus from spreading while also dealing with Ivy's strong beliefs. Another idea is that Ivy discovers a rare plant in Arkham that she believes can save the planet, but it's in a highly guarded and dangerous area. Batman and Ivy might have to work together to retrieve it.
One idea could be a fanfic where Batman and Owlman are forced to team up against a greater threat that endangers both their universes. Maybe a powerful interdimensional villain is causing chaos and they have to put aside their differences.