One alternative could be a fanfic about Boa Hancock's adventures in protecting her island. This can focus on her leadership skills and her love for her people.
Another positive topic could be a fanfic that delves into her past, like how she became the powerful pirate she is today. It can explore her training, her early experiences, and how they shaped her into the character we know, which is much more interesting and positive than inappropriate content.
A fanfic about her forming alliances with other characters in the One Piece universe and how she overcomes challenges together with them would be great. It could show her growth as a character and her ability to cooperate.
There are many great fanfics out there, but ones with inappropriate themes like this are not in line with good taste and ethical standards, so I don't have any to suggest.
A fanfic could explore a friendship between Boa Hancock and Domino. For instance, Domino visits Amazon Lily and is initially met with suspicion but through her interactions with Hancock, they develop a bond. They could exchange stories about their different experiences in the world.
One idea could be a fanfic where Boa Hancock has to team up with her former enemies to face a greater threat. Maybe a powerful new pirate crew that is causing chaos in the Grand Line and she has to put aside her pride for the greater good.
A plot could be centered around a competition. There's a grand tournament in the One Piece world and both Boa Hancock and Domino enter. They compete against each other at first but then realize there's a bigger threat behind the tournament and decide to work together to overcome it. This would involve detailed descriptions of their battles during the tournament and their changing relationship.
The theme of self - discovery can also be present. Hancock might discover new sides of herself because of her relationship with Luffy. For example, she could become more open - minded or learn to trust others more, which is a big step for her as the empress of Amazon Lily.
A big theme is also about breaking barriers. Hancock is a proud and strong woman from Amazon Lily, and Luffy is a carefree pirate. Their relationship in fanfics often shows how they break cultural and social barriers between them. For example, Hancock's tribe has certain traditions and views about men, but with Luffy, she defies some of those. Also, friendship is a theme as Luffy values friendship highly and Hancock becomes part of his circle of friends in a special way.
It would be cool to include some of the other Shichibukai in a fanfic with Boa Hancock. Maybe Doflamingo, and the fanfic could explore the power dynamics and political intrigue between them as two powerful figures in the pirate world. Their different personalities and goals would make for an interesting story.
There may be such a fanfic, but it's not something that I can directly recommend. Fanfics are a very personal form of creative writing. Some people might write a 'Naruto Boa Hancock' fanfic with a lemon aspect to explore different relationships or scenarios. You could try using specific search terms on fanfic search engines. Also, check the reviews and ratings of the fanfics to get an idea of their quality and whether they are something you'd enjoy.
Typically, in a crossover fanfic like this, one main theme could be the exploration of relationships between characters from different universes, in this case, Naruto and Boa Hancock. The 'lemon' aspect might imply a more romantic or sexual undertone, which could be about the development of a passionate relationship between them.
One possible plot could be that Naruto gets lost in the One Piece world and meets Boa Hancock. She is initially distrustful but then realizes Naruto's good heart and they end up working together to fight a common enemy.