BOAC: Spot on!
I'm a private pilot and know how easy it is to become disoriented in IMC at night even when all is well. I also write safety critical software (non aviation) so I also understand the problems in handling real data that may become corrupt/invalid; generally a tidy abort is the best outcome.
Humans are lousy at monitoring automated systems and most automated systems are lousy at giving meaningful error messages, when they eventually FU. The situation that the AF pilots found themselves in IS going to happen again and with future advances in FBW technology it will be even harder for the pilots to trouble shoot.
In an ideal world the human would fly the plane and the computer would monitor his/her performance ... but that's not going to happen ... the bean counters don't like it when our pilot shortens the fatigue life of an airframe with a heavy landing.
Lets not fool ourselves; the ultimate goal of FBW is to facilitate aerodynamically unstable passenger transports with the fuel savings that that would bring. We are in a learning phase; the important lesson that we must learn is that any computerized system has limitations; just like our pilot. The problem is getting our FBW system (when it can no longer cope) to hand over to the pilot efficiently. Herein lies the problem, it can't hand over until it fails; and when its failed it's too late. The pilot needs to know what started the sequence, not the result.
It seems to me that a possible solution would be to provide an independent flight performance monitoring system. It need not concern itself with who is flying (computer/pilot) or provide corrective action. A simple aural 'CFIT in 30 seconds' would be all that was necessary, in the AF case 'airspeed' would have been all they needed to be told to know that things were going south.
I don't know what happened to AF447 but I'm certain that distraction/misinformation would have been a major contributory factor.
And yes, you're right, an independent basic flight control system would have been much more use than a trouble shooting manual.