One idea could be that Harry discovers he has a long - lost sibling who has been living in the Muggle world all this time. This sibling has some unique magical abilities that help turn the tide in the final battle against Voldemort. The new end could be about the siblings uniting the wizarding and Muggle worlds in a way that was never thought possible before.
One idea could be that in this new order, Hogwarts starts accepting students from all magical creatures, not just witches and wizards. This would lead to a whole new dynamic in the school, with different cultures and magic types interacting.
Well, in a 'new normal' Harry Potter fanfic, perhaps the Ministry of Magic decides to open up more to the Muggle world in order to promote better relations. So, Hogwarts starts an exchange program with some Muggle schools. This would bring a whole new set of challenges and friendships. Also, the way Quidditch is played could change. Maybe there are new safety regulations for players, like wearing special protective charms all the time.
One idea could be a new student arriving at Hogwarts. They could be a muggle - born with a very unique magical ability that even the professors are surprised by. This new character could start making friends with the main characters like Harry, Hermione and Ron, and get involved in some mystery that is starting to unfold in the school.
One idea could be the new marauders getting into trouble with a new set of magical artifacts that have been hidden in Hogwarts for centuries. They might discover a map that leads to these artifacts, much like the Marauder's Map. Another could be their interactions with the ghosts in Hogwarts in a more adventurous way, like trying to solve a mystery that the ghosts have been keeping for ages.
One idea could be exploring what would happen if Harry had a twin sister who was sorted into Slytherin. It would add a whole new dynamic to the story, with her having different views and friends than Harry. She could be caught between loyalty to her house and loyalty to her brother.
Often, a new end Harry Potter fanfic brings in elements not present in the original. It could have a darker or more lighthearted tone. Maybe it focuses on side characters more or changes the fate of major villains.
One idea could be that as a girl, Harry has to deal with different social expectations in the wizarding world. For example, she might face more restrictions on certain adventures compared to when she was male. Also, her relationships with Ron and Hermione could change in interesting ways. Ron might be more protective, while Hermione could become a closer confidant as they share more 'girl - specific' experiences.
One idea could be that the new generation discovers a time - turning device left by Hermione. They travel back to the time of the first Triwizard Tournament. There, they meet a young Sirius Black and Remus Lupin, and get involved in the mystery surrounding Cedric Diggory's death in a new way.
In a new end Harry Potter fanfic, it could focus on the long - term consequences of the war. The survivors might have to deal with post - traumatic stress. It could also introduce new magical creatures that play a role in the new ending. Maybe there are some hidden secrets about Hogwarts that are revealed only at the very end, like a secret chamber that has the power to change the outcome of the whole story.
A simple plot idea could be that Ginny is hypnotized by a dark wizard who wants to use her as a weapon against Harry. But Ginny, even in her hypnotized state, resists the dark wizard's commands on a subconscious level.