Well, first of all, it's completely out of character for Luffy. He is a character full of innocence and is mainly focused on his adventures and his crew. Such a fanfiction misrepresents his personality.
There may be some very niche and inappropriate fan creations out there. However, the mainstream 'One Piece' fandom should focus on the real values of the story, like the bonds between the characters, the exploration of the Grand Line, and the various challenges they face. This kind of inappropriate fanfiction is not worthy of promotion.
If it involves sex - related talk, then it's not appropriate as it goes against the family - friendly nature of the original Luffy character and the One Piece series in general.
It's not appropriate at all. These are characters from a well - known story, and creating such sexual fanfiction objectifies the characters and violates the ethical boundaries. We should focus on positive and respectful interpretations of the characters, such as their adventures and friendships.
Well, if the Luffy crew were to meet his mother in fanfiction, it could go in many ways. For one, she might be a strong pirate herself. She could then train the crew in new fighting techniques. Or perhaps she has connections all over the world of One Piece and could introduce the crew to important people. It would surely strengthen the bond within the crew as they learn more about Luffy's family.
No. In the world of mainstream One Piece, such content is not in line with the original spirit of the work which is mainly about adventure, friendship, and the pursuit of dreams. Fanfiction should also uphold positive values.