They could start a magical school of their own. As a married couple, they would pool their resources and knowledge. Hermione's love for learning and Harry's practical experience would make for a great curriculum. They would face opposition from the traditional wizarding schools at first, but eventually prove that their new way of teaching magic is beneficial for young wizards and witches.
One plot idea could be a time - travel fanfiction where they get married in an alternate timeline. Maybe Harry accidentally activates a time - turning device and ends up in a world where he, Ginny and Hermione all decide to have a triple wedding for some magical reason. Another could be a post - war fanfiction where they get married as a symbol of new beginnings and unity among the wizarding community. For example, their weddings could be grand events that bring together all the different houses and factions that were once divided during the war.
One idea could be that they face opposition from some in the wizarding world who still hold onto the traditional views of pure - blood and half - blood relationships. They then have to fight to prove that their love is stronger than these archaic beliefs. Another plot could involve them having to deal with a new dark threat while also planning their wedding, adding a lot of tension and drama to the story.
A plot could be that the Triwizard Tournament tasks are magically altered to target Harry specifically, and Hermione has to use her skills to figure out who is behind it. Maybe a new dark magic is involved that she has to research. She then has to train Harry in new ways to face the challenges. For example, teaching him some ancient spells that are not commonly known.
One idea could be that during a dangerous adventure, Harry realizes his true feelings for Hermione when she risks her life to save him. He then starts to court her in a very Harry - like way, with shy glances and small, kind gestures.
One plot idea could be that they marry in secret to bring peace between the Muggle - born and pure - blood wizarding communities. They face opposition from both sides at first, but their love and determination gradually change people's minds. Another idea is that they are brought together by a magical accident that binds their fates, and as they get to know each other during the process of trying to reverse it, they actually fall in love and decide to stay married. A third idea could be that in a post - war world where everything is in chaos, their marriage is a symbol of hope and a new beginning for the wizarding world.
A really interesting plot for a fanfic where Hermione is Harry's sister could involve the two of them having a shared magical inheritance from their parents that they need to figure out. This could lead to adventures where they explore old family magic. It could also change the dynamic of their relationships with Ron and other friends. Hermione might be more protective of Harry in this scenario, and they could have inside jokes and a deeper understanding of each other based on their family bond.
Well, perhaps in the fanfic, Harry and Hermione find out that the dragons are actually magical guardians protecting a powerful ancient artifact within the tournament arena. They then have to decide whether to compete against the dragons as the rules state or try to work with them to uncover the mystery of the artifact. And also, the dragon that Harry is supposed to face in the tournament could have a special connection to his past that Hermione helps him uncover.
One idea could be a story where baby Harry and Hermione are magically transported to a different time or place. They could be in a magical forest full of strange creatures that they have to befriend in order to find their way back. Another plot could involve them as babies having a special connection that allows them to communicate without speaking. This could lead to them solving small mysteries in Hogwarts even at a very young age. A third idea might be that they are found by a group of magical beings who don't know who they are and raise them with different magical traditions, and later they discover their true identities.
A possible plot is that a spell gone wrong makes Queen's music the only thing that can calm a dangerous magical creature. Hermione, being the clever witch she is, uses her love for Queen to figure out how to tame the creature and in the process, she also uncovers a long - lost magical connection between Queen's music and ancient wizarding magic.
One idea could be a time - travel plot where Hermione goes back in time and teams up with a young Dumbledore to solve a mystery that has implications for the future of Hogwarts. Another could be a story where Dumbledore entrusts Hermione with a special mission that no one else in the wizarding world can handle due to her unique skills and knowledge. Maybe a plot where Hermione discovers a long - lost spell in the Hogwarts library that was created by Dumbledore in his youth, and she has to figure out how to use it to save the school from a new dark threat.