If Harry was Lucius' son, the story would be turned upside down. His appearance might even change, as he'd inherit some Malfoy features. His Hogwarts house would most likely be Slytherin. In the original story, Harry was a symbol of hope for the non - pure - blood wizards. But in this fanfic, he'd start off as part of the pure - blood elite. His relationship with Draco would be a brotherly one, which would be really strange considering how they were enemies in the original. The Triwizard Tournament might not happen as it did, or Harry might participate in it with different motives, perhaps to prove his worth to the Malfoy family rather than for the glory of Hogwarts.
Well, if Harry was Lucius Malfoy's son, it would completely flip the story. Harry would be brought up in a pure - blood supremacist family. He might not have his kind heart as we know it. His relationship with Ron and Hermione would be non - existent or very different. He would probably be taught dark magic from a young age instead of the values he learned at Hogwarts in the original story.
He becomes more conflicted. Growing up as Lucius Malfoy's son, he is exposed to different values. So, instead of the Gryffindor - like straightforwardness, he may have a more calculating side.
One interesting aspect in Lucius and Draco Malfoy's father - son relationship in fanfiction could be Draco's struggle to break free from his father's shadow. Lucius, being a strong - willed and somewhat dark - aligned wizard, has always had high expectations for Draco. In some fanfictions, Draco starts to question his father's values after seeing the destruction caused by the Dark Lord. This leads to internal conflicts within him as he tries to decide whether to follow in his father's footsteps or forge his own path.
She could make the Malfoy family seem more complex. Instead of just being the 'bad guys', with Isabella there could be some internal family debates about right and wrong.
One reason could be for the greater good of the wizarding world. If Lucius is healed, he might be able to turn away from the Dark side and provide useful information about Voldemort's remaining followers.
I'm not sure if there is such a specific fanfic. Fanfic creation is very diverse, but this seems like a rather unusual and perhaps not very common combination. There are many fanfic platforms out there, but this concept might be a bit out of the mainstream.
Harry would likely start off as a rather arrogant character, given the Malfoy upbringing. He'd look down on those he considered beneath him, like muggle - borns. But as he experiences different things, he could start to question his family's beliefs. Maybe he meets a kind muggle - born witch or wizard who shows him that there's more to a person than their blood status. This could lead to a gradual change in his character, from a pure - blood supremacist to someone who believes in equality.
Well, in some fanfictions, Harry might use his advanced magic skills he learned from Dumbledore's old books. Maybe he discovers a long - forgotten spell that can reverse the dark magic effects on Lucius.
One plot idea could be that they are both cursed by a dark wizard and they have to rely on each other to find the cure. This forces them to put aside their differences and work together.
I'm not sure specifically if there are a large number of such fanfictions, but given the vast and diverse nature of the fanfiction community, it's very possible. It could be an interesting concept to explore, as it would completely change the power dynamics, the nature of Harry's relationships with Draco and other characters, and how the wizarding world views him. It might also lead to some really unique plotlines involving the Malfoy family's politics and their role in the wizarding world.