One idea could be that Hermione goes to Romania to study magical creatures and meets Charlie. They team up to save a rare dragon species from poachers. Charlie's expertise in dragons and Hermione's knowledge and quick thinking would make for an exciting adventure.
One plot idea could be that Hermione decides to visit Charlie at his dragon reserve during Christmas. There, they discover a young dragon that's having trouble with the cold weather. They work together to create a magical solution to keep the dragon warm, and in the process, they grow closer. Maybe they also exchange Christmas gifts that have special meanings related to their magical skills and interests.
One idea could be that Hermione, through some magical mishap, ends up in the world of the Twilight series where she meets Charlie Swan. She could use her magic to help solve some of the strange occurrences in Forks that are related to the vampires and werewolves, but has to keep her magic a secret from Charlie at first. They gradually form a friendship as he notices her unique abilities in other ways.
One idea could be that they initially resist the marriage law due to their different worlds in Hogwarts. Charlie is all about dragons and Hermione is focused on academics. But as they start to spend time together, they discover they share a love for magical creatures in a different way. Hermione starts to see the beauty in Charlie's wild dragon - taming ways, and Charlie is amazed by Hermione's vast knowledge which could be useful in dragon conservation.
One interesting plot idea could be that Charlie invites Hermione to study dragons in Romania. There, Hermione discovers a new species of dragon that has some unique magical properties. They have to work together to protect the dragon from poachers. Another could be that Hermione helps Charlie set up a dragon - conservation program at Hogwarts. This would involve getting the approval of the school authorities and dealing with the challenges of having dragons on school grounds.
Perhaps in the fanfiction, Hermione is initially very angry about being paired with Charlie under the Marriage Law. But Charlie takes her to his dragon reserve. There, Hermione sees a different side of Charlie and his passion for magical creatures. This experience makes her more open - minded towards him. Meanwhile, Charlie starts to admire Hermione's intelligence and her determination to fight for what she believes in. Their relationship slowly evolves from forced to something they both cherish.
A plot could involve a magical accident that causes Hermione and Charlie to swap some of their magical abilities. They have to work closely together to reverse the spell. During this time, they learn about each other's strengths and weaknesses and develop feelings for one another.
Their relationship could start as a mutual respect for each other's skills. Charlie admires Hermione's intelligence and Hermione respects Charlie's experience with dragons. As they spend more time together in Romania, they begin to rely on each other more and more, and this could lead to a romantic relationship.
A more complex plot could involve Renesmee being in danger from a new threat in the vampire - human world. Charlie, despite being a human, decides to take matters into his own hands. He teams up with some of the Cullen family members in a way that no one expected. This story could explore the relationships between humans and vampires in a different light, with Renesmee and Charlie at the center of it all.
One idea could be that Charlie discovers a secret room in the chocolate factory that holds the key to a new type of chocolate that can give people the ability to fly for a short time. Another could be that the Oompa - Loompas start a mini - revolution because they want more time off to play their own games. Or perhaps Charlie has a vision of how to make the factory even more magical and Willy Wonka is initially skeptical but then realizes Charlie's idea is brilliant.
One plot idea could be that Hermione, through some magical accident, is transported back in time and meets a young Gellert Grindelwald. She tries to use her knowledge to change his path towards dark magic. Another could be a story where Gellert, in his prison at Nurmengard, has visions of Hermione and they communicate magically across time. A third idea is that in an alternate universe, Hermione is a student at Durmstrang and becomes influenced by Gellert's ideas, but then has to decide whether to follow his dark path or her own moral compass.