This is the BEST idea
You are AWESOME!! Grosse Pointe Blank is one of my very favorite movies (John Cusack could read a phone book and I'd be fascinated)--such awesome neurotic ramblings and worryings, and quick, sly, hilarious dialogue, great banter with Minnie Driver, and a highly satisfying ending. All of you who have never seen it, queue it at the top of your Netflix, get thee to a video store, order it online--it is a wonderful classic. Not to mention it has a great soundtrack--Blister on the Sun is the BEST.
You have made a marvelous transition/adaptation to the world of HP. I love that Harry has decided to become an assassin, and does it very well and almost automatically, but then there's that heart of Harry that Snape knows is still there and manipulates out of hiding by the end. And the banality of the reunion, and the wondrously sexy Severus, dropping those hints all over the place that Harry is usually too gobsmacked to pick up on. The offstage shagging in the infirmary (did people who hadn't seen the movie really get the reference?) was great, although me the pron fan would have liked to be a fly on the wall...
Angelina was great--I loved that magic trashed their computer systems, and the scene when she was taking down the office while bantering with Harry on the phone was great. Also loved that she got to shag the Weasley twins and was in cahoots with Severus all along.
I was hoping for more neurotic sessions with Phineus, and loved that he was also in on Severus's plans. What a manipulative headmaster indeed--who didn't he get in on the plan? Ron and Hermione, check, Angelina, check, spying portrait, check, Harry himself, check. And actually, I suppose he had Confidential in on the plan, too, if she had a contract out on him. And his dialogue was totally hilarious.