Well, perhaps Harry would finally be able to fully focus on his studies at Hogwarts without being held back by any lingering health issues. He could become even more proficient in magic, and might be able to take on more challenging tasks and adventures.
Dumbledore could also be a key figure. He has so much knowledge and wisdom that he might know some ancient magic or spell that could cure Harry. He could guide Harry through the process of getting his health fixed and offer moral support as well.
Well, it could be about Harry having some sort of eye problem, like an injury or a magical curse on his eyes. And then through some means in the fanfic world, perhaps with the help of a powerful wizard or a special spell, he gets his eyes fixed.
Harry is, of course, the main character. Neville could be an unexpected helper. Maybe he has come across a rare herb during his Herbology studies that has the potential to heal eye problems. And Luna Lovegood might also be part of it, with her unique insights and knowledge of the wizarding world's more esoteric aspects, she could offer some unorthodox but effective solutions for Harry's eye problem.
Ensure the conflict is well - defined. In the original Harry Potter books, there was always a clear threat, like Voldemort. In fanfiction, the conflict should be equally engaging. Maybe it's a new dark wizard or a different kind of magical danger. Also, the resolution of the conflict should be logical. It can't be something too far - fetched or too easy. If the characters face a seemingly impossible situation, they should overcome it through their skills, wits, and the help of their friends, just like in the original series.
Hermione could be the one. With her vast knowledge of the wizarding laws and her sharp intellect, she might dig up some old regulations that prove Harry's right to his money. She would then fight tooth and nail in the wizarding courts or against the goblins at Gringotts to get his money back.
In some fanfictions, when Harry Potter gets his letter at 9, it might be a moment of great excitement. It could be the start of his journey into the wizarding world just like in the original story, but with some unique twists added by the fanfiction author. Maybe the owl that delivers the letter has some special markings or behaves in an unexpected way.
Hermione would most likely be involved. She's Harry's best friend and would be eager to help him understand and manage his inheritance. She could use her vast knowledge of magic and research skills to uncover the secrets behind it.
He could work at Flourish and Blotts. He's very knowledgeable about magic, so he could help customers find the right books. It would be a great job for him as he loves to read and study magic. He could also recommend books to young witches and wizards starting their magical education.
Another aspect could be related to his family heritage. Harry could inherit a special magical artifact that was passed down through the Potter family. This artifact might hold the key to some long - forgotten magic or a prophecy. As he explores his inheritance, he uncovers secrets about his family's past and its connection to the overall history of the wizarding world, which in turn helps him in his fight against Voldemort.