One plotline could be that Snape and McGonagall discover a hidden threat against Harry early on. They decide to secretly train Harry in advanced magic that neither Voldemort nor his Death Eaters know about. Snape might use his knowledge of the Dark Arts to teach Harry how to counter the most dangerous curses, while McGonagall focuses on strengthening Harry's Transfiguration skills to help him in combat and escape situations.
Perhaps in the fanfiction, Snape uses a form of legilimency to access Hermione's nightmares. He finds that her nightmares are often a manifestation of her guilt over things she couldn't control in her life, like the fate of some of her friends during dangerous adventures. Snape then helps her to face these feelings head - on. He encourages her to accept that she can't always save everyone and that it's okay to make mistakes. As he does this, the nightmares start to fade, and Hermione begins to see Snape in a new light, not just as a strict professor but as someone who truly cares about her well - being.
One interesting plotline could be McGonagall mentoring a young and troubled student. It would show her nurturing side, which we don't always see in the original books. Another could be her taking on a special mission during the war, like protecting a secret magical artifact. This would highlight her bravery and loyalty to the wizarding world.
Another plotline might involve a time - travel scenario where Harry Potter and Minerva McGonagall have to work together to change an event in the past that is threatening the future of the wizarding world. This could lead to some really cool interactions as they navigate through different eras.
Another plotline could involve how McGonagall deals with Harry's fame. Since she's very no - nonsense, she might shield Harry from the public eye more effectively. This could lead to a Harry who is less influenced by the adoration and more focused on his studies and personal growth.
Well, in some fanfictions, Snape might be trapped in a magical trap set by Death Eaters who are still loyal to Voldemort's ideals. Harry, with his natural sense of justice and his loyalty to Hogwarts (where Snape also has a complex connection), figures out the trap's mechanism and manages to free Snape. Or perhaps Snape is on the verge of being attacked by a magical creature, and Harry, using his experience with magical creatures from Hagrid's teachings, scares the creature away and saves Snape.
One possible plotline could be that Harry, feeling a lack of maternal love in his life, subconsciously starts seeing McGonagall as a mother figure. This could lead to him seeking her advice more often, not just about school matters but also about his personal struggles. For example, he might go to her when he's having nightmares about Voldemort instead of just his friends. Another plotline could be McGonagall initially being taken aback by Harry's behavior but then gradually warming up to the idea. She could start to protect Harry even more fiercely, like a mother bear with her cub.
In some fanfictions, Minerva adopts Harry after realizing the Dursleys are mistreating him. She then takes on the role of a mother figure, which is a huge change for Harry. This could include her taking him shopping for new robes and school supplies in a more loving and nurturing way than the Dursleys ever did. She might also introduce him to the wizarding world in a more personal and gentle way, making him feel truly welcome.
One common plotline is McGonagall protecting Harry from the Ministry of Magic when they wrongly suspect him of something. For instance, if the Ministry believes Harry is using Dark Magic, McGonagall stands up for him, using her influence and knowledge of Harry's character to prove his innocence.
In some 'Snape Adopts Harry' fanfictions, there is a plotline where Snape and Harry have to work together to uncover a mystery at Hogwarts. This mystery could be related to the Dark Arts or some hidden secrets of the school. Along the way, their relationship evolves from a reluctant guardian - ward relationship to a more loving father - son bond. Harry might start to understand Snape's past actions and Snape, in turn, learns to open up and be more affectionate towards Harry.
One interesting plotline could be Snape realizing that Harry is not like the 'Boy Who Lived' (WBWL) as everyone expected. Maybe Harry has a different approach to magic that Snape initially scoffs at but later comes to respect. For example, Harry might be more interested in the darker arts in a way that challenges Snape's views.