One idea could be a story where characters from Earthland are accidentally transported to Edolas in a reversed situation. They could struggle to adapt to the different magic rules and social structures there. For example, Natsu might find that his fire magic works in a completely different way in Edolas, leading to some comical and challenging situations as he tries to figure it out.
Another plot could revolve around a secret connection between an ancient artifact in Earthland and a powerful force in Edolas. A group of Fairy Tail mages could embark on a quest to discover this connection. This would involve a lot of exploration in both worlds, facing various enemies and making new allies along the way. They might have to solve riddles and overcome obstacles that are unique to each world.