Jaune is the character who has been expelled, so he is central to the plot. His character might be dealing with feelings of betrayal, confusion, and a desire to clear his name. The OC, on the other hand, could be a very unique individual. They might have their own goals and motives that initially seem separate from Jaune's situation. But as the story progresses, their paths become intertwined. For example, the OC could be a healer who decides to help Jaune because they sense his innocence, and their relationship develops from there.
Another plot could be that the OC is an outcast too, for different reasons. When Jaune is expelled, they find common ground. They could then decide to leave the place together and start their own journey. Along the way, they learn more about each other's pasts and develop a strong bond while also trying to find a way to prove Jaune's innocence in the events that got him expelled.
It could be Salem herself if the fanfiction focuses on Naruto trying to stop her evil plans. Since Salem has a long history of causing chaos and destruction, Naruto would see her as a force to be reckoned with and try to oppose her.
You can try fanfiction.net. It has a large collection of fan - made stories from various fandoms, including Sabrina x Salem fanfic. Just use the search bar and type in the relevant keywords to find what you're looking for.
One idea could be a story where Sabrina and Salem go on a magical adventure together through different time periods in the magical world. They could encounter various mythical creatures and have to use their combined powers to overcome challenges.
Rather than seeking fanfiction with inappropriate relationships like this, you could explore other positive and healthy relationship - based fanfictions in the same fandom. There are many great stories out there that focus on friendship, adventure, and positive character development.
One possible plot could be that they start off as rivals in Beacon Academy. Cardin is his usual bully self at first, but as he gets to know 'female Jaune Arc', he starts to see her in a different light. They could be paired together for a mission and through that, they learn to trust and rely on each other, slowly developing feelings.
One common theme could be the relationship development between Pyrrha and Jaune. It might explore how their personalities interact in unique situations.
I'm not aware of specific 'female Jaune Arc x Cardin' fanfics off the top of my head. You could try searching on fanfic platforms like Archive of Our Own. They usually have a wide variety of fan - created works based on different pairings.
A common theme is power. Since Salem is such a powerful figure in RWBY, many fanfictions explore how the male reader either gains power through their relationship with her or is in awe of her power. For example, in some stories, the male reader might learn dark magic from Salem.