Another interesting plot could be a natural disaster hitting the area where the General Hospital is located. The hospital staff has to deal with a large influx of patients, shortage of supplies, and their own personal fears. This would show how they come together, or in some cases, fall apart under extreme pressure.
One idea could be that Bella is a new nurse in the hospital and she discovers a secret patient who has a mysterious illness. She then teams up with a brilliant but reclusive doctor to try and solve the mystery.
One idea could be a story where a character from Fairy Tail is injured and ends up in a hospital in a foreign land. They meet a mysterious healer there who has a connection to an ancient Fairy Tail magic. Another could be that the hospital is actually a front for an evil organization that is stealing the magic of Fairy Tail members who come for treatment. Or perhaps a Fairy Tail mage has to use their magic in creative ways to heal the sick in a hospital that's short on supplies.
Well, he could be in the hospital because of a curse. While there, he starts to form a bond with a young patient who has no family. Sirius then decides to protect this child and in the process, uncovers a plot against the wizarding world that has some connection to the hospital. Or perhaps Sirius is in a coma and his friends use magic to enter his mind in the hospital. They find out things about him they never knew before.
One idea could be a story where a new, mysterious illness spreads in the school and the Hospital Wing is overcrowded. Harry and his friends try to find the cause while also helping Madam Pomfrey. Another could be a story about a student who has a special power that is only revealed when they are in the Hospital Wing due to an accident.
Perhaps a group of Fairy Tail wizards visit the mental hospital as part of a community service mission. They discover that some of the patients are not actually crazy but are under the influence of a curse or a forgotten magic spell. The wizards then have to find a way to break the spell without causing chaos in the hospital, all while dealing with the hospital's strict rules and the skepticism of the staff.
One idea could be that Percy starts seeing strange things in the mental hospital that are actually manifestations of Greek monsters from his past. Maybe he has to convince the doctors and other patients that he's not crazy while secretly fighting off these threats.
Another plot idea is that there's a new disease outbreak in the hospital, and there are suspicions of foul play. Ema, with her scientific knowledge, starts to investigate. She could find evidence that points to a pharmaceutical company trying to cover up their faulty product. The Ace Attorney characters then come in to fight for justice in the courtroom based on the evidence Ema provides.
Well, a cool plot could be that Percy, as the General of Kronos, discovers a hidden power within Kronos' forces that could either save or destroy the world. He then has to race against time to figure out how to control this power. Also, there could be a sub - plot where Percy is constantly in conflict with his old Percy Jackson values while leading this new role. Maybe he has to find a way to reconcile his past self with the General he has become.
One plot idea could be exploring General Grievous' backstory before he became the feared cyborg general. Maybe how he was chosen or modified, and his initial reactions to the transformation. Another idea is a story where General Grievous forms an unlikely alliance with a Jedi who realizes they have a common enemy. It could lead to some intense moral and strategic dilemmas for both characters.
One idea could be an OC who is a healer in the hospital and has to deal with the unique injuries of RWBY characters. For example, they might struggle to heal a Grimm - inflicted wound that has some sort of dark magic attached to it. Another idea is an OC that discovers a new type of Dust - based medicine in the hospital, which could revolutionize the way injuries are treated in the RWBY world. And also, an OC who is a patient in the hospital and has amnesia, and throughout the fanfiction, they slowly regain their memories and realize they have a special connection to the RWBY universe.