Yes, it can be a common theme. In many Harry Potter fanfictions, Harry has a strong connection to Hogwarts. Since he has so many adventures there and it becomes like a second home to him, the idea of him 'owning' it in some metaphorical sense, like having a special influence or a deep-rooted place in the school's future, is a popular concept among fanfiction writers.
Yes, it could be. Hogwarts is a very important place in the Harry Potter world, and Harry Potter is the main hero. So it makes sense that protecting Hogwarts by Harry is a popular theme.
Once, in the Harry Potter Hogwarts Battle Game, a strange glitch occurred. As the players were battling a horde of Death Eaters, suddenly the game's graphics distorted. The walls of Hogwarts started to ooze a black, slime - like substance. The characters' spells backfired, and instead of hitting the enemies, they were hitting their own team. One by one, the avatars of the players started to disappear into the darkness, leaving only their screams echoing in the virtual halls of Hogwarts.
Yes, it can be. Many fanfiction writers like to explore unique perspectives, and having Hogwarts as an observer or an active part in Harry's life stories can be very appealing. It allows for a different take on the familiar storylines.
Luna Lovegood could be a main focus. Her unique perspective on magic could be used to discover new magical phenomena that emerged after the battle. She might also be helping the other students deal with their post - battle stress, using her calm and dreamy nature to soothe them.
Well, a plotline might revolve around the new relationships that form. For example, Neville could start a herbology club and meet a new love interest who is also passionate about plants. Also, the wizarding world might see some political changes. Maybe there would be a new Ministry of Magic with more inclusive policies after the dark times of Voldemort's regime.
One really scary scenario could be that the Hogwarts castle itself turns against the players. The staircases start to shift in a way that makes it impossible to navigate. Portraits on the walls come to life, not to give helpful advice but to taunt and mislead the players. Ghosts of the most malevolent wizards start to chase the players, and the Room of Requirement becomes a trap where the door closes behind the players and fills with a deadly, dark mist that slowly consumes their virtual selves.
He might focus on rebuilding Hogwarts. After all the destruction, it would be a huge task and he could use his influence and skills to bring it back to its former glory.
Maybe a jealous student from Slytherin who wants to get back at Harry Potter and his friends. This student discovers a dark and forbidden spell that creates a bondage effect. They start using it on the Hogwarts Express to cause chaos and make Harry and his friends look bad. They see themselves as an antagonist because they feel wronged by Harry and his group in some way, and this is their way of getting revenge.