Hermione could be developed by having her gain some of Slytherin's traits, like his cunning and resourcefulness, in a way that doesn't compromise her Gryffindor values. She could use these new - found traits to solve problems in Hogwarts. Salazar Slytherin's character could be developed by making him more relatable. For example, if he had a love interest in the past that influenced his views, and Hermione discovers this through her research in the fanfiction.
Their relationship could develop uniquely if FemHarry has a secret she's afraid to share, but Hermione, with her sharp intellect, figures it out. This could lead to a deeper level of trust between them. For example, FemHarry might be related to a dark wizard in her past, and Hermione's acceptance of her despite this would strengthen their bond.
One reason could be her thirst for knowledge. Slytherin was known for his cunning and knowledge of magic. Hermione might be drawn to his intellectual side. Another reason could be a desire to break the traditional house rivalries. By becoming a fan of Slytherin, she could promote unity among the houses.
Yes, there are likely some fanfictions out there. In the Harry Potter universe, Hermione is a Gryffindor, but fanfiction often likes to play with the idea of characters having different allegiances or interests. Some writers might explore a scenario where Hermione has an unexpected admiration for Salazar Slytherin, perhaps delving into the history and values of Slytherin house that she could potentially respect, despite the traditional Gryffindor - Slytherin rivalry.
One plot idea could be that Hermione discovers a long - lost spellbook of Salazar Slytherin. As she delves into it, she starts to understand his view of magic in a new way. Maybe the spells in the book are different from what she has learned before, and she has to struggle with whether to use them or not, given Slytherin's somewhat dark reputation.
For Hermione, you could develop her character by having her be more conflicted about the use of magic. Meeting Gellert, who has such extreme views on magic and power, could make her question her own Hogwarts - taught values. For Gellert, instead of just being the 'evil' character, show his more human side. Maybe he has regrets deep down. For example, Hermione could find a way to communicate with his past self and see his early dreams that were not so dark.
Their relationship could develop through Harry's exploration of Slytherin's past. For example, if Harry finds Slytherin's old diary and starts communicating with a remnant of Slytherin's consciousness. They could start off as distrustful but gradually come to understand each other as Harry learns about Slytherin's true motives for creating Slytherin house.
A fanfiction could depict Hermione being magically bound to Salazar Slytherin's spirit. They are forced to work together, and Hermione has to find a way to communicate with him. It would be interesting to see how she reacts to his archaic views and tries to change them while also dealing with the challenges of the magical bond.
There are definitely some out there. For example, in some fanfictions, Hermione might find an ancient artifact that was once Salazar Slytherin's and it unlocks a whole new side of her. It could be that she discovers she has some Slytherin - like traits that she didn't know about before, and the fanfic could then explore how she deals with that in the context of her Gryffindor identity and her relationships with her friends at Hogwarts.
Their relationship could be developed through a shared love of transfiguration. Hermione could seek out McGonagall for extra lessons and in the process, they bond over the beauty and complexity of the subject.
Hermione can be shown as an integral part of the Weasley family. For example, she could participate in their family traditions like the annual Weasley Christmas celebration. By being involved in these special family moments, her bond with them grows stronger.