One thing that troubles me about the FAA approach is not so much the variation in working standards of the MIDO (we know here that your relationship with your DLS - CAA Design Liaison Surveyor, can make or break a project, or even a company) is that all they are really checking is build/maintenance quality.
In my mind, airworthiness is a much more complex problem than that, and unless some kind of design and operating procedures review takes place in addition to that, there's a serious flaw in the system.
G