Harry might develop a different set of values. Flitwick has his own way of looking at the wizarding world. Under his care, Harry could grow to value knowledge and magical finesse more than he does in the original story. This could lead to a Harry who is more diplomatic and less impulsive when dealing with other wizards and witches.
Well, in fanfiction, Flitwick could be portrayed as having a deep understanding of ancient protective magic. He might use this knowledge to create a sort of magical perimeter around Harry. He could also enlist the help of other magical creatures or objects within Hogwarts that are known for their protective qualities. For instance, he could get the help of the house - elves, who have their own brand of magic that could be used to keep Harry out of harm's way. And he may constantly be on the lookout for any signs of danger directed at Harry, using his magical senses to detect any malicious intents.
On the other hand, he could become more powerful and confident in his magic earlier. Walburga might push him hard in his magical studies, and with her knowledge of the Black family's magical heritage, Harry could develop a more assertive and perhaps even a bit of an arrogant streak in his magical abilities. But at the same time, he would also have to deal with the internal conflict of the Black family's dark past.
Harry would probably be more empathetic towards non - human magical creatures. The Mosasaurus is so different from the usual magical creatures he encounters at Hogwarts. He would understand the needs and feelings of these large and perhaps misunderstood creatures better, which could change his approach to dealing with all magical creatures in general.
Perhaps Flitwick discovers Harry has a natural aptitude for a particular type of magic that is not commonly taught. So he takes it upon himself to train Harry privately. This could lead to Harry having a special role in a future conflict, like being able to counter a dark magic spell that no one else can because of this special training.
Harry could also become more refined in his manners and social skills. The Greengrass family is likely to have a certain level of propriety and sophistication, which would rub off on Harry. He may learn to interact more gracefully with the upper echelons of the wizarding society.
Harry's character could change in terms of his confidence. Growing up with the Delacours, he may have more exposure to high - profile wizarding events and people. This could boost his self - assurance. He may also become more open - minded as he experiences different magical cultures. Instead of just relying on what he learned at Hogwarts, he would have the Delacour family's knowledge to draw from. And he might develop a more flamboyant side to his personality, influenced by the Veela - like qualities of the Delacours.
It could strengthen Harry's relationship with the Hogwarts faculty. Since Flitwick is taking the time to train him, Harry might feel more connected to the school and its teachers. This could lead to him having more support from the faculty as a whole.
Harry would likely become more confident under Amelia Bones' care. Since she is a strong - willed and capable witch, her guidance would give Harry a sense of security. He might develop a more strategic way of thinking, influenced by her experience in the wizarding world.
Newt's calm and somewhat eccentric nature would rub off on Harry. Harry, who has faced so much turmoil and danger, could learn from Newt's ability to find peace in the study and care of magical creatures. This could make Harry more level - headed and less impulsive in his decision - making, especially when it comes to dealing with threats like Voldemort. Newt might also encourage Harry to think outside the box. For example, instead of always using traditional magic to solve problems, Harry could start looking at solutions from the perspective of magical creatures and their unique abilities.
Well, it would completely turn the story on its head. In the original, Snape is an adult figure and often at odds with Harry. But if Harry were to raise Snape, perhaps Snape would grow up with a different view of Harry. He might not be so bitter and resentful. Harry could instill in him values that would make Snape less likely to be drawn to the Dark Arts. This would also mean that the whole Hogwarts dynamic would change. Snape might be a much more positive influence on the students instead of the intimidating figure he was in the original story.