There's 'Smoker's Dilemma'. In this fanfic, Smoker is constantly conflicted between his duty as a marine and his growing understanding of Luffy's ideals. It's really interesting to see how their relationship develops over the course of the story.
Another theme is friendship development. Since they start as adversaries, many fanfictions show how they slowly become friends or at least respect each other more. For example, they might find common ground in protecting the innocent or in taking on a powerful villain.
First, understand the characters well. Luffy is carefree and driven by his dreams, while Smoker is strict and upholds justice. For the 'lemon' part, if you want to add a romantic or more adult - themed element, do it in a way that is in - character. Maybe start with building a unique plot where they are forced to interact in a new way, like being stranded on an island together.
A great Smoker x Luffy fanfic stands out when it explores their ideological differences. Luffy is all about freedom and adventure, while Smoker is a marine with a sense of justice. When a fanfic delves into how they can coexist or even learn from each other, it becomes really engaging.
The rescue could be a turning point where Luffy and Dragon begin to collaborate more. Luffy might offer the help of his pirate crew to the Revolutionary Army in certain situations. They could exchange stories and experiences. Luffy could tell Dragon about his adventures on the Grand Line, and Dragon could share his insights about the corrupt world and how they can work together to change it. This would lead to a deeper understanding and a more complex relationship between them.
In the fanfiction scenario where Dragon saves Luffy, it could start a whole new arc. Luffy might be injured badly when Dragon arrives. Dragon could then take Luffy to a secret revolutionary army base to heal. During this time, Luffy could meet other revolutionary army members who could teach him new skills or give him knowledge about the secrets of the Grand Line or the Void Century. This encounter could also strengthen Luffy's resolve to become the Pirate King and at the same time, make him more aware of the larger political struggle going on in the world of One Piece.
Well, in most cases, Luffy would use his unique abilities. He might use his Gum - Gum Pistol to knock out the bad guys. His superhuman strength and speed would allow him to reach Nami quickly and stop the assailants before any harm could be done. Luffy's sense of justice and loyalty to his crewmates are so strong that he would not let anything bad happen to Nami.
One example could be a story where Luffy and Smoker are forced to team up during a strange pirate - marine alliance situation. In this fanfiction, their initial animosity slowly turns into mutual respect as they face a powerful common enemy. The 'lemon' aspect might be subtly added with some underlying romantic tension that builds between them during their adventure.
A possible plot is that Fem Luffy accidentally gets involved in one of Smoker's investigations in a new island. She initially seems like a hindrance to him, but as the story progresses, they find out that there is a much larger conspiracy at play that involves both the Marines and some powerful pirate groups. They have to work together to expose the truth, and during this time, a strange friendship starts to form between them.
Their relationship could start as one of mutual distrust. Smoker sees Fem Luffy as a pirate and Fem Luffy sees Smoker as a Marine who might try to arrest her. But as they face common enemies and challenges, they gradually start to respect each other. For example, if they are both trying to stop a mad scientist from creating dangerous weapons on an island. Through this shared goal, they see each other's strengths and the relationship moves from distrust to a sort of grudging respect.