Well, perhaps a character is in a hurry to get to the guild for an important event and crashes their car. This accident causes them to lose their memory temporarily. The other guild members then have to help them regain their memory and also figure out what was so important about the event. It could lead to some really heartwarming and comical moments.
One idea could be that Percy, Annabeth, and Grover are in a car on their way to a new demigod camp when they get into a crash. Percy uses his water powers to protect them from the worst of it. Maybe the crash was caused by a monster in disguise that was trying to stop them from reaching the camp.
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.
You can create suspense by making the readers wonder if the characters will survive the car crash. For example, end a chapter right as the car is about to hit something. Another way is to introduce a mystery element, like there's something strange about the crash that seems to be more than just an accident, maybe it was magically induced.
Perhaps there's a dark secret hidden in the academy's history. A group of students accidentally stumbles upon it and has to work together to either keep it buried or expose it, depending on what they find out. Along the way, they face many obstacles and learn more about themselves and their magic.
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 Ichigo arrives in the Fairy Tail world and his powerful spiritual energy is mistaken for a new type of magic. He could join forces with Natsu and the gang to fight against a common enemy that threatens both his world and the Fairy Tail world. Another could be that Ichigo's zanpakuto has some sort of unique interaction with the Fairy Tail magic, like being able to absorb or nullify certain spells.
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.
One idea could be Carla getting lost in a mysterious magical realm and the Fairy Tail members have to search for her. This could lead to new friendships and alliances as they explore the unknown area.
One idea could be a new team emerging during the GMG with unique magical abilities that no one has seen before. They could bring a whole new dynamic to the competition.
One idea could be to focus on an alternate origin story for a main character in Fairy Tail. For example, exploring how Natsu's past could have been different and how that would change his relationships in the guild.