Trouble with that notion is that anything you can buy from said sources can be done with a computer and synced over. So blocking such access does nothing.
All iOS apps have FairPlay DRM. Even if you managed to sync to the stolen iPhone, Apple could prevent the apps (and iTunes purchased TV shows, movies, books, etc) from running.
DRM actually working for the consumer, not the other way around.
We are already seeing new Find My iPhone features with iOS 6 where you can actually track your stolen device. I wouldn't surprised if some implementation of what I'm proposing comes with future OS releases.