How hard would it be to make an external analysis tool?

It'd be pretty nice if Riot implemented something into their existing client, or released a standalone piece of software that allowed players to go over replays and spectator games, complete with shared video controls (play, pause, etc), annotation options, screenshot capability, and a google docs style note sheet.

Having to use google hangouts or skype really sucks. Especially since replays are in a proprietary format. (Why not mp4?)

It'd be pretty great to be able to sit down after a game with my buddy and open up the "Analysis tool" or whatever and sit through the replay and be able to talk to each other about how we can improve, and draw on the screen, and take notes and such - and save the session for later viewing if we so desired.

It seems like with replays and spectator mode, most of the functionality is already implemented in the game. Just need to combine it all and put a nice UI over it with some bells and whistles.