One interesting plot development could be Severus having to adjust his teaching style at Hogwarts. Since he has adopted Harry, he can't be as harsh as he used to be towards him in class. This would create a new dynamic between them at school. Also, Severus might have to deal with the other teachers' reactions to this new situation.
In some of these fanfictions, an interesting plot development could be Severus having to deal with the boys' different personalities. Harry, being brave and impulsive, while Draco is more reserved and proud. Severus has to find a way to balance their needs. For example, when it comes to their magical education, he might have to teach them in different ways. He could also have to handle the outside world's reaction to him adopting both a former 'enemy' (Harry) and a pure - blood Slytherin (Draco). Another aspect could be how the boys form a bond with each other through Severus' influence. They might start to see past their initial differences and become like brothers, which changes the whole dynamic of the wizarding world they live in.
Severus could become more confident. With Harry's support, he may not be as shy or withdrawn as in the original story. He might be more open to making friends outside of Slytherin.
Severus' character undergoes a major transformation. He begins to value relationships more, especially his newfound father - son relationship with Harry. He may start to interact more with the other students in a less intimidating way because he realizes that being harsh all the time isn't good for anyone, especially Harry. He also becomes more involved in the non - potions aspects of Harry's life at Hogwarts, like helping him with his other studies or dealing with bullying from other students. This shows a side of Severus that was previously hidden, a side that cares deeply for someone other than himself.
One interesting plot could be Severus initially struggling to connect with Harry due to their past differences. But as he gets to know the extent of Harry's abuse, he becomes fiercely protective. He starts teaching Harry advanced magic privately, which helps Harry grow both in confidence and power.
One possible plot could be that Snape, out of a sense of guilt or a newfound understanding of Harry's situation, decides to take him in. Snape would have to deal with Harry's grief over his parents and his own complex feelings towards the boy. He might start to teach Harry magic in a more personal and different way than at Hogwarts, leading to a unique bond between them.
Well, one interesting plot could be Harry seeing Severus in a new light. He realizes that Severus was actually a complex and misunderstood character. So, he decides to adopt him to give him a new start in life. Another plot might involve Severus initially being resistant to the idea of being adopted by Harry, but over time, he warms up to the concept as he sees Harry's genuine kindness.
One interesting plot could be Severus having to deal with Harry's fame at Hogwarts while trying to keep their new family relationship a secret. It adds a layer of mystery and tension.
Well, it could start with Severus being a vampire in secret and Harry gradually finding out. Maybe Severus initially resists the urge to feed from Harry but then some situation forces him to. For example, he might be injured and need Harry's blood to heal.
In this fanfiction, Severus might adopt Harry to protect him from the dark forces that are still lurking around. He would use his knowledge of the dark arts and potions to keep Harry safe. He could also introduce Harry to a different side of the wizarding world, one that is more about academic study and self - discovery. For example, he may encourage Harry to study advanced potions at a very young age, which would give Harry an edge in his future magical education.
One possible plot could be that Severus discovers the extent of Harry's abuse at the Dursleys. He decides to take Harry in out of a sense of duty or perhaps a hidden soft spot for the boy. He then has to teach Harry about magic in a more personal and nurturing way, different from Hogwarts. They might also face opposition from the wizarding community who question Severus' motives.