A common plotline is Draco trying to reform the Slytherin house. As Headboy, he realizes that the negative reputation of Slytherin needs to change. So he starts implementing new rules and activities within the house to promote unity and positive values.
One great fanfiction about Draco Malfoy as Headboy is 'The Headboy's Duty' on FanFiction.net. It shows Draco taking on the role with a new sense of responsibility. He has to deal with the challenges of Hogwarts in a more mature way, and it also explores his relationships with other students in a really interesting way.
A third plotline could be Draco's struggle with his identity. He has the memories of his previous life, but he's now in Draco's body. He has to deal with Draco's family expectations, his reputation at Hogwarts, and at the same time, he wants to do things differently. This internal conflict could lead to a lot of character development and new story arcs.
One interesting plotline could be that after a strange magical accident, Harry discovers he is pregnant. Draco, initially shocked, gradually feels a sense of protectiveness towards Harry. They have to hide this from the wizarding world which is full of prejudice. Another could be a spell gone wrong during a duel that results in this unexpected situation, and they then must work together to figure out how to deal with the physical and emotional changes, all while still being at odds with their respective friends and families in Hogwarts.
One possible plotline could be Draco trying to hide his squib status from his family. He might go to great lengths to fake being a wizard, like using magic - like tricks or relying on others to do magic for him in front of his family. Another plotline could be Draco befriending other squibs and forming a sort of underground community where they support each other and try to prove their worth in the wizarding world. Or, he could be discovered as a squib by his enemies, like Harry Potter and his friends, and instead of the usual animosity, they feel pity and try to help him come to terms with his new reality.
One possible plotline could be Fem Draco Malfoy having to team up with Harry Potter on a secret mission in Hogwarts. Along the way, they start to see each other in a new light and develop an unexpected friendship that gradually turns into something more. Their different backgrounds and personalities create a lot of interesting dynamics.
There could be a fanfiction where Scorpius and Draco go on a magical adventure together. Maybe they discover an ancient magic that was lost for centuries and have to keep it a secret from the wizarding world. This would explore their relationship as father - son and their courage in the face of danger.
Well, one unique plotline is when Draco and Harry are forced to work together on a secret mission for the Order of Phoenix. They have to put aside their differences and learn to trust each other, which is a complete turnaround from their usual rivalry in the original books.
A common plotline is the discovery of the sister. She might be found in an unexpected place like a muggle orphanage or a hidden wizarding community. Another plotline is her relationship with Draco. At first, they might be at odds because of their different upbringings, but later they grow closer.
One idea could be a story where Scorpius discovers a long - hidden family secret that Draco has been trying to protect him from. It could involve some dark magic from their family's past.
A plotline could involve Draco's family trying to hide his non - pure - blood origin for generations. When Draco finds out, he could start to question his family's values and actions. He might then try to find out who his non - pure - blood ancestors were and what their story was. Maybe he forms an unlikely alliance with some non - pure - blood characters in Hogwarts as he tries to come to terms with his new identity. There could also be a plot where the discovery of his non - pure - blood status changes his relationship with Harry Potter. Instead of being rivals, they could become allies as Draco realizes the unfairness of the blood - based discrimination in the wizarding world.