If you've read Calvin and Hobbes, my conclusion after about half of Book One: Hermione==Susan, and the book would be funnier if Harry were Calvin.
I can just picture him rubbing his hands together. "Unlimited power! The world is mine! Bwahahahahah!" He'd be *so* cross to be fated to be a good guy... Plus, imagine *Calvin* with magic. He has the precise mix of imagination and disregard for studying that'd make him a very, very dangerous wizard to everybody around.
Also, he'd be the only one with a walking, talking
Maybe Voldemort couldn't kill the boy because he was *worse* than him...