If Luffy were a girl in a fanfic, the Straw Hat Pirates' dynamic could shift. The male crew members might be more chivalrous towards her, which could either help or hinder the group at times. For instance, they might be overly protective during battles, but it could also lead to a stronger sense of unity as they all feel the need to safeguard their captain.
The story could also change in terms of the alliances Luffy makes. Other pirate crews or kingdoms might view a female Luffy in a different light. Some might be more willing to ally with her because they see her as a symbol of change or a new kind of pirate leadership. Others might underestimate her and that could lead to some interesting plot twists where she has to constantly prove herself.
One possible idea for a fanfic where Luffy is a girl could be that she has a different approach to leadership. Instead of the brash and straightforward style, she might use her charm and a more empathetic side to bring the crew together. For example, she could be more in tune with the emotional needs of her crewmates like Nami and Robin, and this could lead to deeper and more meaningful relationships within the crew.
His leadership style could change significantly. In the original, he leads with his heart and by example, but in a dark fanfiction, he could be more of a dictator - like leader within his crew, making decisions without much input from others and demanding strict obedience. His goals might also shift from just finding the One Piece and having a grand adventure to seeking power for more self - centered reasons, like revenge or dominance.
If Luffy and Nami got married in a fanfiction, it could change the story in many ways. Their relationship would become more of a central focus. The Straw Hats might be more cautious in battles to protect their new family unit. Also, Nami could have more influence on Luffy's decisions, guiding him with her intelligence. For example, when deciding which island to visit next, Nami's opinion would carry more weight.
If they had a baby, Hancock would become more protective not just of Luffy but also of their child. Luffy would have a new sense of responsibility. He might not be as reckless as before, at least when it comes to the safety of his family. Their relationship would deepen as they share the joys and concerns of raising a child in the dangerous world of One Piece.
When Luffy meets Shanks again in the fanfiction, it might change the story in several ways. For one, Luffy could get new directions or insights from Shanks. This could lead the Straw Hat crew to a new island or a new adventure. Also, Luffy's crew might gain new allies through Shanks' connections. And Luffy's resolve to become the Pirate King could be strengthened even more, which would drive the story forward with more determination.
At first, their relationship might be a bit tense. Luffy is a carefree pirate, while Dragon is a serious revolutionary. But as they start to talk, they could find common ground in their desire to fight against injustice. Luffy's simple and direct approach to righting wrongs might earn Dragon's respect, and their relationship could gradually turn into one of mutual admiration.
Luffy's rubber ability might not change directly due to time travel, but his understanding of how to use it could be enhanced. For example, if he travels to a time where there are different fighting styles, he could incorporate new techniques. Robin's ability to sprout body parts on any surface could be used in really creative ways. If they travel to a time with different architecture, she could use the structures to her advantage in combat or for exploration in ways she hadn't thought of before.
His core personality might not change much. Luffy is still likely to be as carefree and adventurous as ever. However, he might become a bit more sensitive to certain things, like how people treat girls. He'd still be fearless in the face of danger, but could use his new form to his advantage in different ways, like when dealing with female characters who might be more likely to trust a girl.
Luffy would probably still value his friends above all else. However, as a Celestial Dragon, he might have more power at his disposal. This could make him a bit more confident in his actions, but also more responsible. He might feel the need to use his influence to protect not just his crew, but also the oppressed people he meets, in a more official way.
In a One Piece fanfic, an OC (Original Character) as Luffy's rival could be really interesting. This OC might have a unique Devil Fruit ability that directly opposes Luffy's powers. For example, if Luffy has the Gum - Gum Fruit which gives him stretchy abilities, the rival could have a hardening or shrinking ability. This would create intense battles between them as they fight for different ideals on the Grand Line.