Maybe Harry decides to go rogue because he's tired of the Ministry's interference. He could form his own group of like - minded wizards and witches to fight against the corruption in the wizarding world. This would involve him recruiting friends and allies, and facing many challenges along the way.
Another plotline could be that Harry goes rogue after believing he's been betrayed by those closest to him. He embarks on a journey to find the truth, encountering various dark forces and having to rely on his own wits and magic skills. He might also have to make some difficult moral choices during this time.
One interesting plotline could be Harry making new friends at Stonewall who have different magical abilities than those he knew at Hogwarts. This could lead to new adventures and challenges.
One interesting plotline could be Harry going back in time and preventing certain tragedies from happening in the wizarding world. For example, he might stop the death of his parents. Another could be him using his future knowledge to change the way Hogwarts is run, like improving the curriculum for Defense Against the Dark Arts.
One possible plotline could be Harry making new friends at Durmstrang. He might meet students with different magical abilities and cultures compared to Hogwarts. Another could be Harry facing new challenges in the Durmstrang curriculum, which might be more combat - oriented or have different magical theories.
Perhaps there's a plot where Harry discovers a hidden magical mystery within the walls of Harvard. It could be related to an ancient artifact that has some connection to the wizarding world. He then has to use his magical skills, but also his newfound knowledge from Harvard to solve it.
One possible plotline could be Harry's initial shock and confusion upon arriving at the Hellmouth. He might have to quickly adapt to the new and dangerous environment filled with demons and other supernatural threats.
One interesting plotline could be a new adventure where Harry discovers a hidden lemon - themed magical object that has some unexpected powers. It might lead him on a journey to uncover the origin of this object and how it relates to the wizarding world.
In some fanfictions like this, Harry Potter could go crazy because of a powerful dark magic curse. This curse might make him see his friends as enemies and vice versa. He could then start a series of chaotic events at Hogwarts, like trying to attack his best friends. Another idea is that Harry discovers a new type of magic that is so different from what he knows that it drives him to the brink of madness as he tries to understand and master it.
Well, in some 'Harry goes to Marauders time' fanfictions, a great plotline is Harry trying to prevent certain tragedies. He might attempt to stop the betrayal of one of the Marauders, knowing how it will all end in his own time. Also, his relationship with Lily and James could be a major part of the story. He could be the one to give them some advice that changes their fate, like how to better protect themselves from Voldemort.
One possible plotline could be Harry making new friends at Beauxbatons. He might meet students from different backgrounds and cultures, which could lead to some really fun and unique interactions. For example, he could learn new magic spells that are specific to Beauxbatons' curriculum.
Perhaps in this Irish fanfiction, Harry goes to school and discovers a hidden Irish wizarding tradition related to divination. This could involve a different way of reading the stars or tea leaves that is specific to Irish magic, which adds a new dimension to his magical education.