A really interesting plot could be a time - travel scenario. A Fairy Tail wizard somehow ends up in the past of the Star Wars universe, during the Clone Wars perhaps. They could get involved in the conflict, befriend some of the Jedi or even help Anakin Skywalker avoid his fall to the dark side. In return, the Jedi could teach the wizard some new skills related to the Force. Or, a Star Wars character could be transported to the Fairy Tail world and has to adapt to the magic - based society. They could use their technological knowledge to help Fairy Tail in a time of crisis, like when facing a powerful dark guild.
Imagine a plot where the Star Wars and Fairy Tail universes are merging. Characters from both start to appear in each other's worlds randomly. This causes chaos as the rules of both worlds collide. For example, a Jedi might be shocked to see magic being used so freely in Magnolia, and a Fairy Tail wizard might be scared by the presence of Stormtroopers. The two groups would then have to work together to find a way to stop the merging or at least learn to co - exist in this new, mixed - up world. They could also exchange knowledge and skills, like the Jedi teaching the wizards about lightsaber combat and the wizards teaching the Jedi about different types of magic.
One idea could be to explore the backstories of the dragons more in - depth. Maybe show how they came to be involved in the wars in the first place. For example, there could be an ancient prophecy that led to their conflict.
One idea could be that the fallen star is actually a powerful wizard from a different dimension who has lost their powers during the fall. They end up in the Fairy Tail world and have to team up with the guild members to regain their powers and find a way back home. Another plot could involve the fallen star being a magical object that holds a great secret, and Fairy Tail members race against an evil guild to discover and protect it.
One idea could be to focus on a character who discovers a new and rare Star Dress form. For example, Lucy could find a Star Dress that has powers related to an ancient celestial spirit. This would lead to her having to learn how to control it and facing challenges along the way as she tries to master the new powers.
One plot idea could be Aquarius getting lost in the human world. She accidentally gets separated from the Celestial Spirit World and has to find her way back. Along the way, she teams up with some of the Fairy Tail members who are initially skeptical of her but then realize she's not as bad as they thought. Another idea is that Aquarius discovers a hidden power within herself that she didn't know she had. This power could be related to a long - lost magic that was once prevalent in the Celestial Spirit World. It could put her in danger as there are forces that want to control this power.
One idea could be exploring the backstories of the clone troopers in more detail. Maybe focus on a particular clone and his relationships with his brothers. Another could be creating a new adventure for Anakin Skywalker during the Clone Wars that wasn't shown in the original series. For example, he could be sent on a secret mission to a planet that has a powerful and ancient Sith artifact.
One idea could be focusing on a young clone trooper who discovers he has unique Force abilities. He then has to hide this from his superiors while trying to figure out what it means.
You could write a 'Fairy Tail Fanfic' where the magic system is completely different. For example, instead of having different types of elemental and non - elemental magic, there's only one type of magic but different levels of mastery. Or a fanfic that focuses on the relationships between the guild members in a romantic aspect. Like a love triangle between Gray, Juvia, and a new character.
Well, you could write a 'a fairy'a tail fanfic' about a time - travel adventure. Maybe the characters go back in time to prevent a great disaster that was hinted at in the original series. Or perhaps a story where the Fairy Tail guild has to team up with their arch - enemies to face a common, much greater threat. And a simple but interesting idea could be a day - in - the - life story of one of the guild members, showing their normal routine as well as some unexpected events.
Well, a cool plot for a 'Fairy Tail x Fate fanfic' might be centered around a powerful magical artifact that exists in both universes. The characters from both series start to search for it, and during their journey, they learn about the similarities and differences in their magic systems. Maybe some of the Fairy Tail wizards get mistaken for Servants at first and have to prove their true identity while also dealing with the various factions in the Fate world.
One idea could be that your OC is a guardian of a long - lost magical artifact from Fairy Tail's history. They have to protect it from a dark guild that wants to use its power for evil. Maybe they team up with some of the main Fairy Tail characters along the way, like Natsu and Lucy, and there are epic battles to keep the artifact safe.