Yes, there are some out there. You can check fanfiction websites like Archive of Our Own. There might be various stories exploring the relationship between Luffy and Margaret in different ways, such as adventures they go on together or how they interact within the One Piece universe.
There are indeed. One might depict how Luffy's carefree nature and Margaret's more reserved self could come together in a story full of friendship and mutual understanding. Another could be a more action - packed fanfic where they team up to face a common enemy. You just need to search around and read the summaries to find the ones that appeal to you.
A possible plot could be that Luffy and Margaret get married by accident. Maybe during a big celebration on an island, there's some kind of misunderstanding with local marriage customs. And then they have to figure out how to deal with this new situation while also facing threats from pirates or other enemies who might want to use their new relationship against them.
Another place to look could be some dedicated One Piece fan forums. Sometimes, fans share their own fanfictions on these forums. You can also ask other fans if they know of any good luffy x margaret fanfictions. They might be able to point you in the right direction or even recommend their favorite stories.
A possible plot could be that Margaret gets into trouble with a powerful pirate group. Luffy comes to her rescue and then they decide to travel together for a while. During this time, Margaret learns about Luffy's dreams and they support each other in achieving their individual goals. They might also encounter some strange islands and have to work together to survive on them.
I really like the fanfic titled 'Love on the Grand Line: Luffy and Margaret'. In this story, their relationship starts off a bit rocky. Luffy doesn't quite understand Margaret's ways at first, but as they go through various adventures together, they start to fall in love. It has some really cute moments, like when Luffy tries to pick flowers for Margaret in a very Luffy - like clumsy way.
Luffy's appetite could be an interesting trait to play with in the fanfiction. Margaret Lemon might be initially shocked by how much he eats but then find it endearing. Her own kindness and empathy could be explored as she tries to understand Luffy's past and the reasons behind his actions. This could lead to a deeper connection between the two characters as they learn more about each other.
One possible storyline could be an adventure where Luffy and Margaret Lemon team up to find a hidden treasure. Margaret Lemon's unique skills, perhaps her knowledge of ancient maps or languages, could complement Luffy's determination and strength. They might face various pirates and obstacles along the way, and through their journey, they develop a deep friendship.
I'm not sure exactly who Margaret is without more context from the '600 lb life margaret's story'. But she is likely a person who is the focus of this particular story within the '600 lb life' series, probably someone struggling with obesity.
Her promotion of birth control made her a rebel. In the context of her time, such topics were not openly discussed. But she defied the norms and pushed for women to have access to information and means of birth control.