Another plotline might be a 'what if' scenario. What if Snape had managed to befriend the Marauders? It could show how different Hogwarts would have been, and how Snape's life might have taken a more positive turn. It could involve them working together on some magical project or against a common enemy.
One interesting plotline could be exploring Snape's early interactions with the Marauders. Maybe it shows how his enmity with them truly began. For example, it could focus on a particular incident in their school days that was a turning point.
A great plotline is when fanfiction delves into how Snape's relationship with Lily affects his interactions with the Marauders. Since he loves Lily and she is friends with the Marauders, it creates a complex dynamic. In some fics, Snape might try to protect Lily from the potential harm that could come from the Marauders' more dangerous pranks.
Perhaps a plot where Severus discovers his demigod heritage and has to balance it with his life at Hogwarts. He could struggle with how to use his new - found powers without drawing too much attention, while also dealing with his complex relationships with other characters like Harry Potter.
One interesting plotline could be the protagonist using Snape's knowledge of potions to create new and revolutionary brews. For example, they might discover a potion that can heal previously incurable dark magic wounds. Another plotline could involve the character trying to change Snape's fate in the wizarding world. They could attempt to prevent Snape from getting involved in certain dangerous or tragic events, like his involvement with the Death Eaters in his youth. Also, there could be a plot where the reincarnated character uses Snape's occlumency skills to uncover hidden secrets in Hogwarts that were previously unknown.
Well, 'Snape Among the Marauders: A Different Perspective' is also a great one. It gives a new view on Snape's relationship with the Marauders. It might show how Snape's early experiences with them shaped his later life. And then there's 'The Marauders and Snape: Unlikely Bonds' which could be about how unexpected friendships start to form between them in a Hogwarts that's facing some kind of internal turmoil.
One interesting plotline could be Snape and Harry having to work together on a secret project for Dumbledore. They start off distrusting each other but as they face challenges, they gradually become friends. For example, they might be researching a powerful dark magic spell that Voldemort is after, and in the process, they learn about each other's past traumas and start to empathize.
Some fanfictions have a plotline where Snape survives the Battle of Hogwarts and he and Harry have to deal with the aftermath together. They might have to face the wizarding community's reaction to Snape's past actions and also work on rebuilding Hogwarts. There are also stories where Harry, while still at school, starts to understand Snape's difficult position between Dumbledore and Voldemort and tries to help him in some way, which creates a whole new dynamic between them.
Perhaps a plotline where Snape's heart leads him to question his loyalty to Voldemort. As he becomes more in touch with his emotions, he realizes the true horror of the Dark Lord's actions. This could lead to him secretly working against Voldemort in a more direct way than in the original story. He may also find himself in the middle of a moral dilemma as his new - hearted self clashes with his past actions.
One interesting plotline could be Harry growing up with Snape's guidance and inheriting his potions skills at an early age. He might have a different dynamic with the other Hogwarts students, being more of an outcast due to his connection to the often - misunderstood Snape.
One interesting plotline could be Snape going back and trying to prevent the death of Lily Potter. He might use his knowledge of the future to change certain events that led to her demise.
Some fanfictions have a plotline where the OC is a healer who is called to Hogwarts to deal with an epidemic of a magical illness. Snape is initially skeptical of her methods, but as she starts to make progress, he becomes more interested in her work and in her as a person. This kind of plotline allows for a lot of character development for both Snape and the OC, and also shows the different aspects of the wizarding world's medical and magical practices.