One common theme is the power of friendship. Since both Hermione and Percy are intelligent and ambitious, their friendship can be explored in terms of how they support each other's goals. For example, Hermione might help Percy with his Ministry - related work, while Percy could offer Hermione academic advice.
One great Hermione Granger and Percy Weasley fanfiction is 'The Ministry Project'. In it, they team up to reform some of the Ministry's archaic policies. It shows a side of Percy that we don't often see in the original books, his more idealistic side that Hermione can really relate to.
You can start by looking on popular fanfiction websites like Fanfiction.net or Archive of Our Own (AO3). Fanfiction.net has a huge collection, and you can simply search for 'Hermione and Percy Weasley' in the search bar. AO3 also has a great tagging system which makes it easier to filter the stories based on your preferences, such as genre or rating.
Their personalities. Percy is ambitious and rule - abiding, while Hermione is intelligent and also has a strong sense of justice. Some fans see potential in how their different traits could interact and create an interesting dynamic in a relationship.
One common theme is redemption. Percy has made some mistakes in the series, and in fanfiction, Hermione can often be the one to help him find his way back, which is a form of redemption. Another theme is the clash of different personalities. Percy is more formal and structured, while Hermione is highly intelligent but also more emotional at times. Their interactions based on these differences can create interesting stories.
Writing fanfiction about such a disturbing and inappropriate topic as rape is unacceptable and violates basic moral and ethical standards. So, it should not exist and I would not support or promote any such content.
Their different personalities. Percy is all about order and following the rules, while Hermione is also rule - abiding but in a more independent - minded way. In fanfiction, this contrast can lead to some great character development and interesting interactions as they learn from each other.
One popular theme is intellectual partnership. Since both Hermione and Percy are highly intelligent and academically - inclined, many fanfictions explore them working together on projects, like researching ancient magic or reforming the wizarding education system.
One great fanfiction could be 'Hermione and Percy's Hogwarts Adventures'. It delves into how their friendship might have developed outside of their normal friend groups. It shows Percy helping Hermione with her studies in a more detailed way than in the original books, and Hermione in turn helps Percy loosen up a bit.
Draco Malfoy could be a great antagonist. Even after the war, he might still hold some grudges against Hermione, and Percy's new - found progressive ideas could clash with Draco's traditional pure - blood views. He could try to undermine their projects or spread false rumors about them.