Maybe Harry uses magic to create a unique zoo. He could have magical creatures from the wizarding world, like hippogriffs and unicorns. The zoo would be a place for both wizards and muggles to learn about these amazing beings.
One possible plot could be that after the war, the Ministry of Magic is in shambles. Harry Potter, being a hero, is given Azkaban as a form of trust. He then discovers that there are dark forces still lurking within the prison, and he has to fight them off while also trying to reform the prison system.
Hermione could be a major character. She would be really helpful with all her knowledge, maybe helping Harry with the care of the magical creatures and coming up with ways to educate the visitors. Ron might also be there, perhaps handling the more physical tasks around the zoo like building enclosures for the larger creatures.
One possible plot could be that Harry, having a deep love for Hogwarts, decides to take over the school to reform it. He might introduce new courses like advanced defensive magic for all years. He could also focus on improving the living conditions of the house - elves, making Hogwarts a more inclusive and progressive place.
One plot could be that Harry has to defend his ownership of the Luna fanfiction against those who want to claim it for themselves. This could lead to a series of adventures and magical battles within the fanfiction world.
One possible plot could be that Harry, after defeating Voldemort, decides he wants to do something different. He uses his Triwizard Tournament winnings to start a broomstick - making business. He teams up with some of the best broomstick makers in the wizarding world and creates a new line of broomsticks that are faster and more maneuverable. However, he faces competition from established broomstick companies who try to undermine his business.
The fanfiction could be about Harry turning the island into a sanctuary for magical creatures. He might find some endangered or mistreated magical creatures and bring them to the island to live in peace. He'd then have to deal with the challenges of taking care of them all, like finding food sources and creating habitats suitable for each species.
Perhaps he'd own a company that specializes in magical artifacts. He could discover new uses for old artifacts or even create new ones. For example, he could develop a new type of invisibility cloak that has additional features like being able to change colors to blend in with different environments. His knowledge of magic and his adventures would give him great insights into what wizards really need in terms of artifacts.
Perhaps in the fanfiction, the zoo becomes a secret sanctuary for magical creatures that are endangered in the wizarding world. The zookeepers are actually wizards in disguise, and Harry Potter and his friends discover this while on a school trip. They then have to help protect the sanctuary from dark wizards who want to use the magical creatures for evil purposes. This plot would combine the muggle and wizarding worlds in an exciting way.
Maybe Harry discovers a new type of snake with magical abilities. For example, it could be a snake that can turn invisible at will. This would be really cool as it could add a new dimension to the wizarding world's magical creatures.
Well, perhaps the plot could involve Harry using his magical knowledge to sell unique magical items in his shop. He might have a special section for potions, with rare ingredients sourced from all over the wizarding world. And he could use his fame from his adventures to draw in customers, like young witches and wizards who want to hear his stories while they browse through his wares.