On the topic of Harry Potter and reimaginative fan-fiction, there's Harry Potter and the Methods of Rationality, in which Harry is reimagined as a science- and technology-savvy rationalist.
It also, IMO, has better and fairer treatment of the houses than the canon, which I felt was pretty reductive. (Gryffindor good, Slytherin evil, the other two may as well not exist.) I think the books would have been better to have, say, Hermione in Ravenclaw, Ron in Hufflepuff, and Harry in Gryffindor. The only thing that would have had to been dropped was the silly "Gryffindor wins the house cup every year" bit.