One idea could be that the blind son of Artemis is a seer in a different sense. Instead of seeing the future with his eyes, he has prophetic dreams. These dreams could be very vivid and detailed, but also confusing at times. He has to learn how to interpret them and use this gift to help his fellow demigods. Percy could be skeptical at first but then come to rely on his insights.
One common theme is the idea of adaptation. Since Percy is blind, the fanfictions often focus on how he adapts to his demigod life. For example, he has to learn to fight monsters without relying fully on his sight.
Friendship is also a big theme. His friends support him through his challenges. For example, Grover might use his empathy link with Percy in a new way to help him out. It shows how their bonds are strengthened in difficult times.
There could be many interesting storylines in such a fanfiction. Maybe the blind son of Artemis has special powers that compensate for his lack of sight. For example, he could have an extraordinary sense of hearing or smell, like being able to sense the presence of monsters from a great distance just by the sound of their growls or the smell of their sulfurous breath. He might also have a special connection to nature, being able to communicate with animals in a unique way, asking them for help or information.
There's also 'A Blind Hero's Journey'. In this fanfic, Percy's blindness adds a whole new layer to his adventures. It's interesting to see how his other senses develop more and how he uses them to fight monsters. It has some really cool battle scenes that are unique because of his blindness.
One great Percy Jackson blind fanfiction is 'A New Perspective'. It explores how Percy has to adapt to his blindness while still dealing with his demigod duties. The story really dives deep into his character development in this new situation.
Grover can be a key character too. In some 'Percy Jackson blind fanfic', Grover uses his empathy link with Percy in a unique way to assist him. His loyalty to Percy is further emphasized in these stories.
Artemis is a must - as the goddess leading the Hunt. Her hunters, especially those like Phoebe, could be main characters. Phoebe could be curious about Percy and his blindness. She might be the one to first approach Percy when he's found. Another character could be Chiron. He could hear about Percy being with the Hunt and come to check on him. He could offer advice to both Percy and the Hunt, based on his vast knowledge of demigods. And then there's the Oracle. It could give some cryptic prophecy related to Percy's new situation with the Hunt, which would add an interesting layer to the story.
One possible plot could be that Percy, being blind, has a unique connection to the Hunt. Maybe he can sense their presence in a different way. For example, he can feel the magic of the Hunt through vibrations in the ground or changes in the air. The Hunt could be initially suspicious of him but then realize his special abilities are actually an asset. They could take him under their wing and he could help them in their quests in ways no one else could, like using his blindness to his advantage in stealth missions.