Wow, what an idea!
For mind games, have you read The Other by Thomas Tryon? The best ghost/horror story I have ever read.
It would be a great twist, especially if they had filmed the ending at the time of the first movie when Harry was a little boy. At the same time, very sad.
Maybe Ron & Hermione were neighborhood kids he had never actually met, just seen out the window. They could do a lot with all the characters.
I'll have to check out The Other. Thanks!