A possible plot could involve her going on a quest. Maybe she's the only one who can decipher an ancient prophecy related to Athena, but she has to first overcome the doubts of her fellow demigods who are not used to a trans girl being in such a central role. Along the way, she discovers new powers or aspects of her identity that are linked to both her being a daughter of Athena and her trans experience. She might also form unexpected alliances with other outcasts in the demigod world.
It could be about her struggle to fit into the demigod world while also dealing with her identity. For example, she might face challenges in Camp Half - Blood where the traditional ideas of gender roles among the children of Athena exist. She could be trying to prove herself as a strategist and a daughter of Athena while also being true to her trans identity.
You could check out Archive of Our Own (AO3). There are often many unique fanfics in the Percy Jackson fandom that might feature a trans girl daughter of Athena. Just search for relevant tags like 'Athena' and 'trans girl' and you'll likely find some interesting reads.
One possible plot could be a story of cooperation. Maybe there is a great threat to the world of the Greek gods, and Athena, with her wisdom, and Poseidon, with his power over the sea, have to work together. They could start off distrusting each other due to their past rivalries, like the competition for Athens. But as they face challenges, they gradually learn to respect and rely on one another's strengths.
Well, it could be about Naruto having some of Athena's powers or wisdom passed down to him. Maybe he uses these new abilities to face stronger enemies in the Ninja world. For example, he might have enhanced strategic thinking like Athena, which helps him in battles and in making alliances.
A great plot could be a competition between them in the modern world. Athena, known for her wisdom, and Aphrodite, for her beauty, could compete in a talent show. Athena shows off her intellectual skills while Aphrodite wows with her charm. But as the story progresses, they realize that they both have more to offer than just their main traits and learn to respect each other.
A possible plot could be that Athena and Janey discover a hidden vault. Along the way, they face off against a new gang of bandits who are also after the vault's treasures. They have to use their wits and skills to overcome the bandits and reach the vault first.
The plot might involve a power struggle too. Since Poseidon and Athena both have their own domains and powers. In the fanfic, their love could be a way to combine their powers or it could be something that threatens the balance of power among the gods. For example, other gods might sense the change in their relationship and try to use it for their own gain.
Another reason might be as a form of punishment or lesson. Athena, being the goddess of wisdom, could be teaching Percy something about seeing the world from a different perspective. By turning him into a girl, he might gain new insights into how females are treated in the world of the story, whether it's in the demigod community or among mortals.
One common theme is self - acceptance. Trans girl characters often struggle to accept themselves in these fanfics. For example, they might be dealing with body dysphoria at the start and then gradually learn to love themselves.
One possible plot could be that Athena and Aphrodite are in a competition that involves lemons. Maybe they are competing to see who can use the lemons in the most creative way to bestow a certain kind of beauty or wisdom upon a mortal. For example, Aphrodite might try to use the lemon's acidity to create a potion that enhances physical allure, while Athena could use it to make a concoction that sharpens a mortal's mental faculties.
The plot might involve Percy trying to bring peace between Poseidon and Athena. There could be some ancient feud between them that Percy is determined to end. He could start by finding common ground between the two deities in their respective domains, like the sea and wisdom. Along the way, he would face many obstacles, including other gods and goddesses who don't want the peace to happen.