I think this is a good idea too, but probably Construct is still so new that it would be outdated very quickly. For now it seems to make more sense to leave it all online so it can be updated easily and often.
Edit: Although maybe it would make a lot of sense to put some sort of offline help feature that would walk the user through answers to a lot of common questions. Maybe like a FAQ. It would all be fairly basic, information that's already available online. But maybe it would reduce the number of times the admins have to encourage newbies to go through tutorials, etc.