Why, exactly, is a black Hermione "needed?"
Or a black Severus Snape?
Or inevitably, a black Harry Potter?
Or an all black cast?
Why is it necessary?

I'm not familiar with the universe but aren't there supposed to be other wizarding schools out there, such as one in Africa? Why not tell original stories about a boy wizard from that school in your fanfiction television shows? What's stopping them?