If they redid the HP movies just stick closer to the books and don't add stuff in for the main male and female leads into the movies that weren't in the books and don't take out so much that events later on seem to come out of nowhere to many people...don't change who said what and when and such like they did...
If they did that they'd probably get people complaining about how much they'd changed the movies and all...only to then be informed that the remake was actually closer to the books than the Original movies were...
And actually it does matter that Harry is in Gryffindor, as later on Dumbledore tells him that Harry's choices are what set him apart, he chose to not be in Slytherin and that mattered in the end. The houses do matter actually...if you change a movie taken from a book that much then why not just make up your own story as the movie that came out would little resemble the book and basically be a new story...