One great Severus Snape and Minerva McGonagall fanfiction is 'The Unlikely Alliance'. In this story, they are forced to work together on a Hogwarts project. Their different teaching styles and personalities create interesting interactions. Snape's brooding nature contrasts with McGonagall's more no - nonsense approach, and as they overcome obstacles in the project, they also start to understand each other better on a personal level.
Another trope is the 'mentor - mentee' dynamic in reverse. Usually, they are both mentors to students, but in some fanfictions, they end up learning from each other. Snape might learn more about emotional openness from McGonagall, while she could learn about some of the darker arts and how to better protect students from Snape. It's an interesting flip of their usual roles.
One idea could be a story where Minerva and Severus have to team up to protect Hogwarts during a new, unexpected threat. Maybe a dark magic artifact is discovered near the school and they must use their combined knowledge and skills to keep it from falling into the wrong hands.
One popular theme is their friendship. Despite their differences, they are both dedicated teachers at Hogwarts, and fanfictions often explore how they might support each other behind the scenes. Another theme is their possible romantic relationships, not necessarily with each other, but how their views on love and relationships might be. For example, Snape's unrequited love for Lily could be contrasted with McGonagall's more reserved approach to love. Also, their roles during the wizarding wars are often explored in fanfictions. How they coped with the danger, made decisions, and protected the students.
For Minerva, you could explore her more emotional side. In fanfiction, show her struggling with her feelings for Severus. Maybe she has always seen him as a difficult colleague, but then realizes there is more to him. For Severus, delve deeper into his loyalty. You can write about how his loyalty to Dumbledore and Hogwarts extends to his relationship with Minerva. For example, he would do anything to protect her when Hogwarts is in danger because she is an important part of what he is protecting.
Their different personalities make it interesting. Snape is brooding and often seen as a bit of an outsider, while McGonagall is strict but fair. The contrast between them gives a lot of room for creative writing. For example, how they handle discipline in their respective houses is very different, and fanfictions can explore the clashes or agreements that might occur.
She becomes more nurturing. Usually, she's known for her strictness at Hogwarts, but when she adopts Harry, she softens up. For instance, she might show more patience when Harry makes mistakes in his magic studies.
There are probably fanfictions out there with this premise. Fanfic authors love to play with the established canon of a story. By making Minerva McGonagall Hermione's mother, they can rewrite many aspects of Hermione's life. Maybe she would have grown up with a different set of values, or her magical abilities could be seen in a new light. It also has the potential to create new conflicts and reconciliations within the Hogwarts community.
One great 'Harry Potter Minerva McGonagall' fanfiction is 'The Transfiguration of McGonagall'. It delves into her early years as a teacher and how she dealt with the challenges. Another interesting one is 'McGonagall's Secret Mission' which shows her on a covert operation during the wizarding war. There's also 'Minerva's Heart' that focuses on her relationships with other Hogwarts staff members.
The world of Harry Potter itself is so rich and detailed. Minerva McGonagall is an integral part of that world. Fanfiction about her allows readers to return to the magical world of Hogwarts. Writers can also introduce new magical elements or storylines related to her. For example, they can create stories about her adventures during her youth, or her role in some new magical crisis that was not part of the original books. This gives fans a chance to experience more of the magic and the character they love.