Hi Wingswinger,
I absolutely agree with you that when everything else has gone horribly wrong having everything manual is a good idea.
However, look at Golden Rule 7 " Use the proper level of automation for the task". We are not a single seat operation and the aircraft has been designed to be flown by a team.
Teaching people to leap straight from full FMS guidance to full manual contol every time they have minor concerns has major drawbacks and can lead to more serious problems as you have just trebled the other pilot's workload and drastically reduced the ability to cross monitor each other, you are also out of the loop. Having the PF take out the AP and Autothrust just to follow the cross like a single seat pilot is a real pain as PNF as you have to do his job as well as your own.
Rule 6 of the Golden Rules does say "Take Over" - but there are 2 levels of control between FMS guidance and fully manual which may be a safer option. Lets say the aircraft is not following the noise abatement properly, you have "taken over" by pulling heading and still kept the PNF in the loop - going fully manual at that point is not the best option, and even if you have to tighten the turn you are better of with the speed being controlled while you overbank. This is what Airbus teaches.
My point was that people do not cascade down from full FMS guidance early enough. Yes it may need to go straight to fully manual ( inadvertent selection of Go Around or stalling for example), but the Airblue 321 would not have crashed if he had just checked it had gone into heading mode on the FMA.