Perhaps in the fanfiction, Snape submits to Harry Potter in terms of teaching methods. Harry, having learned a lot from his own experiences, convinces Snape to try a more hands - on and empathetic approach with the students, leading to a transformation in Hogwarts' teaching environment.
One possible interesting plot could be Snape having to follow Harry Potter's lead in a dangerous mission. Maybe they are in a situation where Snape has no choice but to trust Harry completely, which is a big change from their usual relationship in the original books.
In some versions, Snape might submit to Harry Potter's moral code. Harry, with his strong sense of right and wrong, makes Snape reevaluate his actions and allegiances. This could lead to Snape making amends for his past wrongdoings and joining Harry more wholeheartedly in the fight against the dark forces.
Perhaps in the fanfiction, Snape assigns Harry to clean all the old potion vials in the storage room during detention. While doing so, Harry discovers an old diary that seems to hold secrets about Snape's past at Hogwarts, which then leads to a series of revelations and a change in their relationship.
One interesting plot could be Harry growing up with Snape's strict but ultimately caring guidance. Snape might teach Harry potions from a very young age, and Harry could develop a different kind of magic skill set compared to canon. Another plot could involve Harry having to deal with the Slytherin side of the wizarding world earlier, as Snape has strong Slytherin ties. Also, the relationship between Harry and Snape could be a complex mix of father - son dynamic and teacher - student relationship, which would be really fascinating to explore.
One interesting plot could be Snape raising Harry while secretly training him in advanced potions and dark arts defenses. Harry would grow up with a different perspective on Snape, seeing him as a strict but caring father figure. Another plot might involve Snape having to protect Harry from other dark wizards who suspect Harry's true potential. This could lead to some intense magical battles and Snape using his knowledge and skills to keep Harry safe.
A really unique plot could be Snape adopting Harry during a time when Voldemort is still a threat. Snape has to balance protecting Harry from Voldemort's followers and also from the prejudice within the wizarding community. He might train Harry in Occlumency more intensively, and in the process, they develop a deeper understanding of each other. Harry starts to see Snape not as the mean professor but as a complex person with his own traumas and reasons for his actions.
Well, a possible plot is that Harry discovers his true parentage in a very dramatic way. He could be in the middle of a battle or a difficult situation at Hogwarts and suddenly realize that Snape and Bellatrix are his parents. This would completely change his perception of himself and his place in the wizarding world. He might then have to deal with the consequences of this revelation, such as how the Order of the Phoenix and the Death Eaters view him.
Perhaps in the fanfiction, Harry is magically bound to please Snape in academic tasks. So, he has to study extra hard in Potions class and other subjects Snape is involved in. This might result in a transformation of their relationship, from animosity to a grudging respect as Snape starts to see Harry's efforts.
Perhaps in this fanfiction, Harry submits to Snape in order to gain access to some important information. Snape might be in possession of secrets about Harry's family or his own powers that he refuses to share unless Harry shows complete obedience. So, Harry decides to submit to Snape's demands in order to uncover these mysteries that are crucial for his journey as a wizard.
Obviously, Harry Potter and Snape are the main characters. Harry, with his courage and leadership, and Snape, with his complex past and skills. But other characters like Hermione and Ron could also play important roles. They might be the ones who first notice the change in Snape's behavior towards Harry and help Harry deal with this new situation.
Perhaps she has a special magical ability that is different from her father's. This ability could draw the attention of both good and bad forces. She has to learn to control it while also dealing with the expectations placed on her because of her father. For example, if she has the ability to communicate with magical creatures in a way no one else can, she might be pressured to use it for the benefit of the school or be targeted by those who want to use it for evil.
One possible plot could be Snape getting involved in a risky mission within the wizarding world that somehow involves Harry Potter. Maybe it's a mission to retrieve a powerful and dangerous magical artifact that Voldemort is also after. And Harry, against Snape's initial wishes, tags along and they have to learn to work together, facing numerous magical creatures and dark spells along the way.