Another plot idea is if Hermione turns into a centaur. In this form, she would gain incredible strength and knowledge of the Forbidden Forest. She could then use her new - found abilities to help Hagrid protect the forest and its inhabitants. She might also have to deal with the other centaurs' initial distrust of her, as she was once a human.
One idea could be that Hermione turns into a phoenix. She could then use her new form to fly around Hogwarts, exploring places that are usually off - limits. She might also discover she has the power to heal with her tears, like a phoenix does, and help injured students or magical creatures on the school grounds.
A plot could involve a shape - shifting creature that takes on the form of Draco and Hermione at different times. This causes chaos in Hogwarts as everyone is confused. Draco and Hermione must find a way to stop the creature and in the process, they discover secrets about each other and the magical world that they never knew before. They also start to see each other in a new light, leading to a possible romantic relationship.
It could be a group of pure - blood supremacists. They might see Hermione's transformation as an abomination and try to 'correct' it or get rid of her. They could spread rumors about her and try to turn the wizarding community against her in her new form.
One idea could be a story about a young wizard who discovers a new magical creature in the Forbidden Forest. Maybe it's a small, furry creature with the ability to turn invisible at will. The wizard tries to protect it from being discovered by other, less kind-hearted students or teachers.
One could be the Thestral. Since Hermione is very intelligent and curious, her discovery and study of Thestrals, which are invisible to those who haven't witnessed death, could be an interesting plot. Another could be the Niffler. Hermione might have an adventure trying to keep a Niffler from stealing shiny things in a museum or a wizard's home. And the Phoenix is also a great choice. Hermione could be involved in a story where she helps a Phoenix that is in trouble, perhaps injured or lost, given her kind-hearted nature.
Well, a plot could be centered around Draco the sub creature being wrongly accused of a crime in the magical realm. It has to prove its innocence while also dealing with the prejudice against sub creatures. Maybe there's a mystery element where it has to find the real culprit who is trying to frame sub creatures in general. Or, Draco could be part of a prophecy that only it can fulfill, but first it has to overcome many challenges and the distrust of other magical creatures.
One idea could be exploring how the inheritance affects Harry's relationships with his friends. For example, if he inherits some special abilities from a creature, his friends might react with a mix of awe and concern.
A plot could involve a magical creature that bonds Harry and Voldemort in an unexpected way. For example, a rare faerie that makes them see each other's memories. Through this, Harry discovers some long - hidden secrets about Voldemort's past that could potentially change the course of their enmity. They then have to decide what to do with this new - found knowledge.
You could write a fanfic about a magical creature that can travel through time. It appears to Harry and his friends during their fifth year. This creature is being hunted by a powerful dark wizard from the future who wants to use its time - traveling abilities to change the course of wizarding history in his favor. Harry and his friends must protect the creature and figure out a way to send it back to its own time safely, all while dealing with the normal chaos of Umbridge at Hogwarts.
One interesting plot twist could be that Hermione, as a vampire, still retains her thirst for knowledge. Instead of blood, she discovers a way to feed on knowledge energy. For example, she might visit ancient libraries at night and absorb the knowledge stored in the books, which gives her a different kind of 'nourishment'. Another plot twist could be her relationship with her friends. Harry and Ron might initially be scared of her, but then they realize that she's still the same Hermione deep down. They could then team up to fight against vampire hunters who see Hermione as a threat just because of what she's become.
One idea could be a story where a new creature is discovered and brought to the school. The students have to learn how to take care of it and in the process, they discover new magical abilities related to that creature.