That’s what fanfic is for, and it’s especially the case in Snarry, where we’re really making the two best, most memorable characters in the Potterverse come into their own as fully rounded characters, not mere plot devices. Perhaps I’m being harsh on JKR here, for that is not what she was aiming to do with her books, obviously, but it is a real lack when you read the series, in my most humble opinion.
Truer words were never spoken. In JKR's world, Harry and Severus exist only as tools of the ideas she thinks they represent; she doesn't let them grow. Too bad, because they are such wonderful characters.
I can't wait to read your story. Too bad I can't vote. :)