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 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.
Lucy might also be a suitable main character. Her kind heart would lead her to try and help the other patients. She could use her celestial magic in unique ways to communicate with those who seem lost in their own minds. Maybe she gets trapped in the mental hospital while looking for a lost Celestial Spirit item and has to find a way to escape while also helping those in need.
One idea could be a new character arriving at Fairy Hills and having to adapt to the unique living situation. They could face challenges like getting along with the different personalities of the Fairy Tail mages living there.
A cool plot could be that a powerful artifact in Skyrim is causing chaos and the Fairy Tail members are summoned to find and secure it. Along the way, they meet up with the Dragonborn. Some members might befriend the Dragonborn and help in their battles, while others might be a bit more skeptical and think the Dragonborn is a threat to their own power within the group.
One idea could be that Gojo, with his overpowered abilities, joins Fairy Tail and becomes a mentor figure to the younger wizards. He could teach them new ways to use their magic and help them in battles against powerful foes.
A plot could revolve around a conspiracy within the tournament organizers. They could be trying to manipulate the results for their own gain, and the Fairy Tail members have to figure it out while competing.
A plot could involve Mystogan's past coming back to haunt him. An old enemy from his homeland tracks him down in Fiore. This forces him to face his past mistakes and traumas. Alongside his Fairy Tail friends, he has to find a way to defeat this enemy and finally come to terms with his past.
One plot idea could be exploring Aquarius's past more in - depth. Maybe a story where we see her life before she became a Celestial Spirit. Another could be a story where Aquarius has to team up with an unlikely character from Fairy Tail to save the Spirit World.
Maybe there's a new member who has a secret gangster past. They joined Fairy Tail to start a new life, but their old gangster buddies come looking for them. This causes a lot of internal conflict within the guild as some members don't trust the new person, while others want to give them a chance to prove themselves and fight off the old gang.
One plot idea could be Ranma getting transported to the Fairy Tail world and having to learn magic. Another is a team - up where the characters from both series face a common enemy. Maybe a dark magic user who wants to use Ranma's unique curse for their own evil purposes.