I could see Harry becoming a professor and eventual headmaster way WAY down the line, like after he's, oh, say 50 or so (not entirely kidding). He would be the Dumbledore of his generation. Meanwhile, here's a question - what did Sirius Black "do" post-Hogwarts pre-Azkaban? I think young-adult Harry should team up with Sirius for some adventures; whether they're actual Aurors or not, go out and fight the dark side together.