One interesting plotline could be Luffy making new and strange alliances in the New World. For example, he might team up with a race of sea - dwelling creatures that have unique abilities.
The Yonko would definitely be major antagonists. Since Luffy is in the New World, the likes of Kaido or Big Mom would be natural choices. Their vast power and influence would pose a great threat to Luffy and his crew.
In a Luffy x Nami Lemon New World fanfiction, there could be a situation where Nami is kidnapped by a group who wants to use her knowledge of the New World and the lemons (maybe there are special lemons with unique properties there). Luffy, being the fearless captain, sets out on a solo mission to rescue her. Along the way, he meets some old friends and new allies. When he finally reaches Nami, they both realize their feelings for each other have grown even stronger during this ordeal.
One possible scenario in Whitebeard and Luffy fanfiction could be a story where Luffy, after the time skip, meets an older Whitebeard in a spiritual realm. Whitebeard imparts some of his final wisdom to Luffy, about leadership and protecting one's crew. This could be a very emotional encounter that further shapes Luffy's growth as a pirate.
In a Luffy x Nami Lemon New World fanfiction, Luffy could develop his ability to understand Nami's more complex emotions. The lemons could be a symbol of something precious to Nami, and Luffy has to respect and protect that. He might start to see Nami not just as a crewmate but also as someone he has deep feelings for. Nami could develop her sense of adventure even more. She might be initially cautious about the lemons in the New World, but as she explores more with Luffy, she becomes bolder. Their characters could also grow together as they face new enemies in the New World who are after the lemons. This would test their loyalty to each other and the crew, and they would come out stronger as individuals and as a couple (in a platonic or romantic sense depending on the direction of the fanfiction).
The characters included the male lead, Monchi D. Luffy, the supporting actor, Simon, Zach, and Zagu.
"The World Dominator from Luffy" Author: What I'm attacking is nothing more than a light novel/derivative Doujinshi novel with system style and invincible style elements. It's finished and can be enjoyed without worry.
[User recommendation: Thank you for your invitation. I'm a pirate in the navy. I've just fought Mary Joshua.]
[You have transmigrated into Luffy and obtained the Pengri System.]
On the surface, he was a law-abiding military third generation, but behind his back, he was the ruler of the underground world.
"I just want to live behind the scenes. Why do you want me to be a general?"
[PS: Momosuke must die, and Oda can't stay either!]
I hope you will like this book.
One potential new ally could be a powerful pirate from the past. For instance, a pirate who was known for his great navigation skills. Luffy could use his help to explore uncharted seas more easily.
There could be some of Dragon's comrades in the revolutionary army who become important figures in Luffy's upbringing. For example, a veteran revolutionary who teaches Luffy about the history of the world and the wrongdoings of the World Government.