Well, a great plot idea could be that they are paired by the Marriage Law and have to pretend to be a happy couple in public for some political or social reasons in the wizarding world. But in private, they are constantly bickering. As time goes on, they find that they can't help but fall for each other. They might also face challenges from Draco's old Death Eater associates who don't approve of his union with Hermione.
One idea could be that the marriage law forces them to live together and they initially clash due to their different backgrounds. But as they get to know each other's true selves, they start to respect and even fall in love. For example, Hermione might introduce Draco to the value of Muggle - born magic and he could show her some of the more complex pure - blood magic traditions in a new light.
Maybe the marriage law causes a stir in the wizarding world. Draco and Hermione initially resist but then realize that for the sake of the baby, they need to make it work. The baby might be born with a special gift that is a combination of the Malfoy and Granger magic. They could have to deal with Draco's family not accepting Hermione at first, but the baby becomes the bridge that brings them all together in the end.
One idea could be that due to the marriage law, Draco and Ginny are forced together. At first, they are hostile towards each other because of their past differences. Draco's pure - blood pride clashes with Ginny's Weasley independence. But as time goes on, they start to see the good in each other. For example, Draco realizes Ginny's bravery and Ginny sees that Draco is not as bad as she thought.
A possible plot is that their baby is born with a prophecy attached to it. The wizarding law dictates that any baby with a prophecy must be placed under special protection and observation. Draco and Hermione, being protective parents, try to find a way to ensure their baby's normal upbringing while still adhering to the law's requirements. This could lead to a lot of drama and character development as they face opposition from those who strictly enforce the law.
One idea could be that the marriage law forces Hermione and Neville to get married, but at first they are hesitant. However, as they start to live together, they discover each other's hidden talents. For example, Neville shows his amazing skills in herbology which Hermione admires. They gradually fall in love as they face challenges together, like dealing with the expectations of their friends and family who had different ideas about their relationship.
Maybe in the fanfiction, the marriage law is a ploy by a dark wizard to disrupt the order in Hogwarts. Hermione and Minerva have to pretend to be happily married to fool the enemy. During this time, they learn about each other's insecurities and strengths. Hermione might introduce Minerva to some modern Muggle concepts that could be useful in their fight against the dark forces, and their relationship gradually turns into a real and deep connection.
A plot could revolve around a marriage law that was created to strengthen pure - blood and half - blood relations. Hermione, being a Muggle - born, faces a lot of opposition. Harry stands by her side and they fight against the discriminatory aspects of the law. They could go on a journey to find ancient magic that could nullify this unjust law. Along the way, they meet different characters who either help or hinder them, and their relationship grows stronger as they face these difficulties together.
One plot idea could be the Oc and Hermione having to navigate the complex rules of the marriage law. Maybe they initially resist but gradually find common ground and unexpected feelings for each other. For example, they could be paired together by the law and at first be at odds, but as they face challenges in the wizarding world together, they start to rely on and care for one another.
One idea could be the initial shock and resistance from both George and Hermione. George might be still mourning Fred and not ready for such a sudden arrangement. Hermione, on the other hand, could be conflicted as she had feelings for Ron. They could start off as reluctant partners but gradually find common ground through their shared love for magic and their determination to fight against the unjust law together.
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.