Hermione Granger would likely be a main character. She could use her vast knowledge to help Harry in his efforts to fix Hogwarts, whether it's researching ancient spells for repairs or coming up with new educational strategies.
One interesting plot point could be Harry Potter implementing new and fairer house points systems in Hogwarts. This would change the dynamic between the houses and promote more unity.
I'm not sure of the exact title, but there's a fanfiction where Harry teams up with Hermione to fix a car that has some sort of dark magic attached to it. Hermione uses her research skills and Harry his practical magic skills. Together, they figure out how to remove the dark magic and also upgrade the car's features in a magical way.
Another element could be the interaction between the wizarding world and the Muggle world of cars. Harry might have to hide his magic while fixing cars in the Muggle world, or he could introduce some magical car features that amaze the Muggles. In some fics, there could be a conflict when other wizards don't approve of Harry using magic in such a Muggle - oriented way. This adds drama and tension to the story.
Maybe Draco Malfoy. He could make fun of Harry for trying to fix his hair and try to jinx his attempts, thinking it's a silly thing for Harry to focus on.
In the fanfiction world, Harry might be the heir to Hogwarts if there was some sort of magical pact made generations ago. For example, perhaps one of his ancestors had a special role in the creation or protection of Hogwarts, and this role was passed down through the family. It could also be that his unique magical abilities, like his ability to resist Voldemort's attacks from a young age, are signs of a deeper connection to Hogwarts itself. This connection could be what designates him as the heir in the fanfiction's plot.
One possible reason could be that he was under the influence of a powerful dark magic or a curse that made him lose control. Another reason might be that he was tricked into believing Hogwarts was a threat to the wizarding world in some extreme way. Maybe a powerful enemy manipulated him to think that destroying Hogwarts was the only way to save everyone.
Yes, in many fanfictions, Harry Potter can have special interactions with Hogwarts, like it being a sentient entity he can communicate with. It adds an interesting twist to the story.
One great 'Harry Potter' fanfiction set in Hogwarts is 'The Life and Times' by Jewels5. It delves deep into the Marauders' era and gives a detailed look at the lives of James Potter, Sirius Black, Remus Lupin and Peter Pettigrew. It fills in many gaps in the original story and the characterizations are really well - done.
In some fanfictions, Harry Potter can be depicted as the heir of Hogwarts. Fanfiction allows for a lot of creative interpretations. Writers might come up with unique backstories or plot twists that make Harry the heir, perhaps based on some long - lost family connection or a special prophecy within the fan - created universe.