A great plotline might involve the crew getting lost in a mysterious and dangerous part of the Grand Line. They have to rely on each other more than ever and discover hidden secrets about the world and themselves. Maybe they find an island that has been forgotten by time, with technology or magic that is completely different from what they've seen before. And of course, there could be a lot of character - development moments for all the crew members during this adventure.
One potential new member could be a skilled archer from a forest - dwelling tribe. They have amazing accuracy and can use special arrows made from rare materials found only in their forest. Another could be a mermaid or merman with the ability to control water in unique ways, not just for combat but also for things like navigation and finding hidden treasures.
Obviously, they will support Luffy all the way. He is their captain, and they have complete faith in him. They have been through so much together, and they know Luffy's strength and determination.
In a 'Sabo meets Luffy crew' fanfiction, there could be a lot of emotional reunions. Sabo might share his adventures since they last parted. He could train with the crew members, especially Zoro to exchange sword - fighting skills. And he would surely have a great time reminiscing about their childhood with Luffy.
In this fanfiction, Luffy might be initially in awe of Whitebeard's presence. He could challenge one of the crew members to a friendly spar, like Ace perhaps. And they might share stories about their adventures at sea.
Shanks might interact with Luffy's crew in a very friendly and father - like way. He could pat the crew members on the back, give them words of encouragement, and share his experiences with them.
Fem Luffy would probably bring a lot of energy. She might be more empathetic in some ways compared to the original Luffy, which could help in resolving internal crew conflicts. For example, if two crewmates have a disagreement, she could use her charm and understanding to smooth things over.
Zoro would be deeply affected. He has sworn to follow Luffy and his death would be a huge blow. He might feel like he failed in his duty to protect the captain. He would likely become more withdrawn at first, but then focus on getting stronger to avenge Luffy if there was someone to blame for his death.
If Naruto joined Luffy's crew in fanfiction, there would be a lot of interesting interactions. Naruto is used to a world with different kinds of powers like chakra, and in the One Piece world, there's Haki and Devil Fruits. He would have to learn about these new power systems. Also, his relationship with the crew members would be fun to explore. For example, he and Usopp could probably come up with some crazy inventions together, combining ninjutsu and Usopp's gadget - making skills.
In the fanfiction, Hancock could offer her help to Luffy's crew. Given her strength and influence in Amazon Lily, she could provide valuable resources or information. Maybe she'd teach Nami some self - defense techniques she learned in her own island. Also, there could be some romantic tension between Hancock and Luffy that the crew might tease them about.