Rebecca could potentially be in Luffy's harem. After Luffy helped her in Dressrosa, she might develop feelings for him. She is a strong - willed and kind - hearted character. Another could be Shirahoshi. Luffy has a special connection with her as he saved her from being captured. Her gentle and innocent nature would contrast with some of the other more assertive members of the harem.
One possible storyline could be Luffy and his harem going on adventures together on different islands. They face various challenges, and during their journey, they develop deeper emotional bonds with Luffy. For example, they might help him fight against powerful pirates or discover hidden treasures. Along the way, their relationships grow and there are many heartwarming and exciting moments.
I would recommend 'Ace, Luffy and Sabo: Reunion of Souls'. This fanfiction is full of heart - warming moments. It shows how their past experiences shape their present interactions and how they support each other in the face of difficulties.
I really like the fanfic 'The Bond of Luffy and Hancock'. In this one, their relationship is explored through various challenges they face together. It shows how Hancock's tough exterior softens when it comes to Luffy. There are also some interesting side characters that add depth to the story. Then there's 'Luffy's Impact on Hancock'. This fanfic focuses on how Luffy's presence changes Hancock's world view and how she grows as a person because of him.
I really like 'Luffy and Law's Shared Destiny'. It shows how their fates could be intertwined in a more romantic way. The story has some really sweet moments between them, like when they share their dreams under the starlit sky during a break in their journey. It also adds new elements to the One Piece world they exist in.
Their relationship could develop through mutual respect. Luffy respects Whitebeard as a powerful and respected pirate, and Whitebeard respects Luffy's determination and potential. For example, they could start with a simple exchange of stories about their adventures at sea.
Another theme is rivalry. Zoro and Sanji have a friendly rivalry which can be elaborated on in fanfictions. For instance, they might compete in a friendly tournament on the ship to see who is stronger or more useful in a certain situation.
Zoro could be one. His loyalty to Luffy could potentially turn into something more in a harem - themed fanfiction. Sanji might also be in her harem, given his chivalrous nature towards women and his deep respect for Luffy. Usopp could be another, as he looks up to Luffy and in this context, that admiration could develop into romantic feelings. And perhaps some new characters introduced specifically for the fanfiction, like a mysterious and handsome pirate from a far - off land who is drawn to Female Luffy's unique aura.
One common theme is adventure. Since they are both part of the One Piece world which is full of exploration, many fanfictions have them going on new and exciting adventures together. Another theme is friendship evolving into love. They start as comrades and over time, feelings develop.
There are some really interesting ones. For example, there are fanfictions that imagine how Carrot might fit into the Straw Hat crew in a more permanent way through her relationship with Luffy. These stories often include her learning more about the crew's dreams and helping them achieve their goals, all while developing a special bond with Luffy. Another aspect could be how their different species characteristics interact in the story.