There could be a plot where Snape's muteness is a secret that he tries to hide from everyone at Hogwarts. The story could be about how he manages to teach Potions and be a double agent for Dumbledore all while keeping this secret. Or perhaps a plot where his muteness is a magical experiment gone wrong, and the story is about his journey to reverse it. Along the way, he might discover new aspects of magic and his own identity that he never knew before.
One possible plotline could be that Severus Snape discovers he has royal blood. He then has to navigate the complex world of royalty while still dealing with his duties at Hogwarts. Maybe he uses his new - found status to gain more influence in the wizarding world, but also has to face those who are jealous or suspicious of his sudden rise.
One plotline could be that Snape discovers a long - lost diary of one of the founders, like Godric Gryffindor. The diary reveals secrets about the founding of Hogwarts and some hidden magic. Snape then uses this knowledge to protect Hogwarts from a new threat. Maybe he has to face a dark wizard who is also after the secrets in the diary.
Well, a plotline might involve Snape initially being in denial about the pregnancy. As it progresses, he could start to form an unexpected bond with the unborn child. There could also be a plot where other characters find out and either support him or try to use it against him. Maybe Voldemort discovers it and tries to manipulate Snape in a new way because of this situation.
There could also be a plotline where Hermione discovers some of Snape's past traumas and in trying to help him, they form a bond. Snape, out of gratitude and a newfound respect for her, starts to take care of her like a mentor. He shields her from the harsh judgments of other Hogwarts professors and students alike, and together they work towards a better future for the wizarding world.
One possible plotline could be that Moody discovers Snape is in a dangerous situation due to some dark wizard's plot against him. Maybe Snape is being framed for a crime he didn't commit, and Moody, with his Auror skills and knowledge, believes in Snape's innocence. He then uses his resources and magic to rescue Snape from an ambush or a false arrest. Another plotline could involve Snape being held captive by Death Eaters, and Moody, despite their past differences, decides to rescue him because he realizes Snape is a crucial part of the fight against Voldemort.
One possible plotline could be that Harry breaks a major Hogwarts rule, like sneaking into the Forbidden Forest. Snape catches him and decides that a severe punishment is in order, which in this case is spanking. Another could be that Harry fails a very important Potions test repeatedly, and Snape, frustrated with his lack of progress, resorts to this extreme form of discipline. However, these are all just fan - created ideas and not part of the official story.
The sister could have her own love story intertwined with the events of the wizarding world. She might fall in love with a Gryffindor, which would be a huge scandal in the eyes of some. This relationship could be a source of tension, not only within her family but also in the wider wizarding community. And as Severus tries to protect his sister from the dangers of the wizarding war, her relationship could add an extra layer of complexity to his already difficult situation.
One possible plotline could be that Snape discovers a hidden weakness of Voldemort. Maybe through his years of spying, he finds out that a certain spell, when combined with an ancient magic artifact, can destroy Voldemort. So he devises a plan to get hold of the artifact and uses the spell at a crucial moment when Voldemort is off - guard, perhaps during a major battle when Voldemort is focused on other opponents.
Perhaps Snape is under a spell that makes him act this way towards Hermione. He starts to give her special attention in class, praising her more than usual and even asking her to stay after class for 'private tutoring'. Hermione, on the other hand, tries to figure out if this is really Snape or if there is some dark magic at play. She may start to investigate, which could lead to an adventure of sorts as she tries to break the spell if there is one.
One possible plotline could be the daughter's struggle with her father's complex reputation at Hogwarts. She might face prejudice from students who remember Snape's dark past. Another could be her discovery of her father's true love for her mother, which was hidden for so long. And she could also have a special talent in potions, just like her father, and use it to outshine others in her classes.