There are currently discussions going on with all of the USA CRJ200 operators to try and get the FAA to approve no type 4 on the fuselage. Bombardier has even written a paper stating that the upper part of the fuselage does not need type 4 but the FAA and I think even Transport Canada are the ones holding all of this up. Taking off depressurized isn't that big of a deal, the EMB145 operators have been doing it for 17 years now without any issues. I think this all originates from Bombardier labeling the fuselage as a critical surface so until they change that in all of the manuals nothing will change.