In a fanfiction where Harry is abandoned as a child, there could be a plot where he is left at the doorstep of a powerful magical family other than the Dursleys. This family initially rejects him but then realizes his potential and decides to train him in the ways of dark magic, which he then has to struggle with as he grows up. Another idea is that Harry is abandoned in a magical forest. There, he is raised by magical plants and animals. He develops a special connection with them and uses this connection to create a new form of magic that no one in the wizarding world has ever seen before. Also, he could be abandoned near a wizarding school in another country, and he grows up learning different magical traditions and brings these new ideas back to Hogwarts when he finally returns.
Well, perhaps in this fanfiction, Harry is abandoned as a child and is then taken in by a dark wizard who has his own motives. Maybe the dark wizard wants to use Harry's fame to gain power in the wizarding world. Or it could be that Harry is abandoned and ends up in a parallel magical dimension where he has to find his way back to the normal wizarding world while learning new and strange magics. Another angle could be that he is abandoned and is found by a magical creature, like a centaur, who imparts wisdom and unique magical abilities to him.
One plot idea could be Harry struggling to fit in at first in Slytherin because of the house's reputation for dark magic, but then he discovers the true values of loyalty and cunning within it. He could form an unlikely friendship with a pure - blood Slytherin who helps him see that not all in Slytherin are bad. Another idea is that Harry uses his newfound Slytherin traits to outwit Voldemort in a different way than in the original story, perhaps by using more stealth and manipulation.
Perhaps Harry is adopted by a Muggle family who are aware of the wizarding world. They could be a family of scientists who study magic from a scientific perspective. Harry would grow up with a unique understanding of magic, seeing it both as a wonder of the wizarding world and something that can be analyzed. This might make his time at Hogwarts very interesting as he tries to blend these two views of magic.
One idea could be that the second child discovers a long - forgotten magic spell that has the power to reverse time briefly. This could lead to some interesting adventures where they try to correct past mistakes in the wizarding world. Another idea is that the second child has a special connection with magical creatures that no one else does, and they use this connection to solve a mystery involving a dangerous creature that is threatening Hogwarts.
One idea could be exploring the alternate timelines more deeply. For example, what if Voldemort had actually won in one of those timelines? How would the wizarding world look like? Another could be delving into the relationship between Albus and Scorpius in a more complex way, like their adventures outside of Hogwarts that test their friendship.
Hermione could be a potential rescuer. In a different timeline or scenario, she might stumble upon the abandoned Harry and use her intelligence and knowledge of magic to take care of him. Another could be Hagrid. He has a big heart and a love for all things magical. He might find Harry and take him under his wing, protecting him from any harm. And Sirius Black is also a possibility. Even if he was wrongly imprisoned, if he escaped earlier, he could be the one to rescue Harry and keep him away from the Dursleys.
One idea could be Harry being raised by the Weasleys from a very young age. He'd grow up with their large family dynamic, learning magic in a more chaotic but loving environment. It might change his personality a bit, making him more outgoing and confident earlier. Another plot could be him being raised by Remus Lupin. Lupin would instill in him a deep understanding of the dark arts in a more academic way, and also teach him about acceptance of his own lycanthropy - like condition if he were to inherit it. And a third idea is Harry being raised by the centaurs in the Forbidden Forest. He'd learn their unique brand of magic, which is more in tune with nature, and have a different perspective on the wizarding world and its relationship with the natural world.
A plot idea could be that Harry's reincarnation as Salazar is part of a grand prophecy. As he uncovers this truth, he realizes that he has a greater role to play in the wizarding world. He might start to gather followers who believe in the old ways of Salazar. This could cause a division in the wizarding community, with some seeing Harry as a savior and others fearing that he will bring back the dark and exclusionary ways of Salazar. Harry would then have to decide how to use his new identity for the good of all wizards.
One idea could be that Harry, as Voldemort's soulmate, tries to use their connection to redeem Voldemort. He might show Voldemort memories of love and kindness in an attempt to change his dark ways.
One idea could be that Harry discovers his connection to Morgana gradually. Maybe he starts having strange dreams related to her. As he digs deeper, he finds that some of his powers are actually linked to Morgana's magic, which sets him on a journey to understand more about his heritage and how it affects his role in the wizarding world.
Perhaps the pregnancy causes Angelina to discover new magical abilities within herself. As she is carrying new life, she starts to have prophetic dreams about the future of the wizarding world. This could lead her on a journey to find out more about these dreams and how they might be related to her unborn child.