One possible plot could be that Rogue somehow gets transported to Lucy's world and they have to figure out how to get him back. During this time, they start to understand each other better. Lucy might learn about Rogue's past and his struggles, and Rogue could see the kindness and strength in Lucy. They could develop a friendship or something more as they face various challenges in the Fairy Tail world.
One possibility is that it's a fanfic set in an alternate universe where Sting has a special connection with Lucy. They might discover a new form of magic together. For example, Sting's white dragon slayer magic could combine with Lucy's celestial spirit magic in an unexpected way, leading to a whole new set of adventures.
A possible plot could involve a dark magic that starts affecting Fiore. Lucy discovers some ancient texts about it, and she realizes she needs the help of Sting and Rogue. They go on a journey to find the source of this dark magic. Along the way, they encounter many enemies. Sting and Rogue use their Dragon Slayer magic to fight, while Lucy summons her Celestial Spirits. As they get closer to the source, they find out that one of their old enemies has returned and is using this dark magic to seek revenge. Together, they combine their powers to defeat the enemy and save Fiore.
In the fanfic, Lucy could develop a more adventurous side. Since Rogue is often involved in more dangerous and shadowy things, she might be drawn into that world and have to adapt. For Rogue, being around Lucy could make him more in touch with the positive aspects of the magical world. He might start to question his own darker tendencies and strive to be a better person. This could lead to him making different choices in battles and in his relationships with others.
One possibility is that it focuses on a love story between Lucy and Rufus. They start off as rivals, perhaps competing in a magic competition. But as they get to know each other better, they realize they have more in common than they thought and fall in love. This could involve them sharing their dreams and fears, and overcoming obstacles together to be with each other.
One idea could be that Lucy and Rogue are brought together by a powerful magic artifact. They have to team up to protect it from an evil force that wants to use it for destruction. Along the way, they start to understand each other's pasts and form a deep bond.
In a 'Fairy Tail Lucy becomes a Dragon Slayer' fanfic, it could start with Lucy being in a life - threatening situation. To survive, she unknowingly absorbs the power of a dying dragon. This power starts to change her. At first, she is scared of the changes. But then, with the support of her friends, she decides to embrace it. She then begins a journey to master her new powers. She might learn that her Dragon Slayer magic is linked to a special type of celestial spirit that has dragon - like qualities, and she has to find and bond with this spirit to fully control her powers.
One idea could be a time - travel plot where Lucy, Rogue, and Sting are sent back in time to the founding of Fairy Tail. They have to navigate the early days of the guild while also trying to find a way back to their own time. Another could be a magic - swapping scenario, where they accidentally exchange their magical abilities and have to learn to use each other's magic to fight a new, powerful enemy.
One idea could be that Jackal, after some soul - searching, decides to turn over a new leaf and teams up with Lucy. They could go on a mission to retrieve a powerful magical artifact that was once used by an ancient dark wizard. Along the way, Jackal's knowledge of the dark arts helps them navigate through various traps, while Lucy's celestial magic provides the offensive and defensive power they need.
One possible plot could be that Lucy and Juvia leave Fairy Tail to go on a self - discovery journey. They might want to explore their individual magic powers more deeply without the constraints of the guild. Maybe they travel to different magical realms, meet new characters, and learn unique magic techniques that they can bring back to Fairy Tail later.
One possible plot could be that Midnight uses his magic to trap Lucy in a dream - like world. In this world, he challenges her to various magical tasks. As they interact more, Lucy starts to understand Midnight's past and the reasons behind his actions. Eventually, she manages to break free from the dream world using her Celestial Spirit magic and in the process, Midnight has a change of heart and decides to turn away from his evil ways.