Well, it would probably strengthen his relationship with his friends. His friends would be happy for him to have his parents back, and it could lead to more group activities like family - style outings. For instance, they might all go on picnics together with Harry's parents.
There could also be new characters introduced in the fanfic. Maybe a young, talented wizard or witch who is just starting at Hogwarts and becomes involved in Harry's return journey. They could bring a fresh perspective and new abilities to the story. And of course, Dumbledore, even if he's not physically present all the time, his influence and legacy are likely to play a role, so he can be considered one of the important characters in a sense.
One idea could be that Harry discovers a hidden chamber in Hogwarts that was unknown even to Dumbledore. This chamber could hold secrets about the founders that have been lost over time. Another could be that the students return to find Hogwarts has been taken over by a new dark force that's not related to Voldemort but has its own set of dark magic. Maybe a group of former Death Eaters who escaped justice are trying to create a new regime within the school walls.
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 new character could be a half - giant half - wizard. He's often been an outcast in both the giant and wizard communities. When he comes to Hogwarts, he has to deal with the prejudices of the students and teachers alike. But he also has great strength and a unique perspective on magic. There could also be a character who is a descendant of a former Hogwarts headmaster or headmistress. This character could bring a sense of legacy and new secrets about the school's past.
Perhaps there's a plot twist where the Forbidden Forest reveals a hidden entrance to an ancient magical realm that was previously unknown. This could lead the characters into a whole new adventure, with new magical creatures and challenges that they have to face. It might also hold the key to defeating the remaining threats in the wizarding world.
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.