ILS27LEFT: I tried to avoid unncessary posting there, since the thread is a bit chaotic as is, and if admins decided to keep it as thread and not as a temporary subforum where theories can be discussed in an organized way (and merged into a thread at later point, and moved back to this part of forum), I think it is easy to reduce their workload by posting less. Yet, your post makes me wonder, if it is a good decision or not.
First of all, you ignore some key thing. GPS wasn't lost, since the a/c knew its own coordinates.
GPS isn't useful to calculate airspeed, since you don't know about wings, so GPS signal has nothing to do with airspeed data.
(Even trying to track something that moves with the air would be better indicator for speed... but sadly it would be pretty hard to say the least)
Some people on a hungarian forum suggested, that if you have attitude data and EPR you can calculate the speed, but it would again ignore some of the effects of weather...
Some people suggested metal plates and various devices to determine airspeed, such devices aren't tested or installed, so it doesn't work.
While it is theoretically possible for a computer to calculate some estimated airspeed from various data, and try to help the pilot to keep the a/c in safe limits, it would require some pretty complex computer software, which isn't tested or installed yet. Worst of all: It isn't even implemented in a way that would let us use it on an Airbus FBW aircraft. And measuring if you are withing safe limits can be easier anyway.
The serious faults you speak about are consequences of each other. You also ignore what kind of "serious faults" we are speaking about. If you count the alternate law message, the autopilot and autothrottle messages, etc. as serious faults, not simple consequences of pitot icing, then it could make sense.
But you also gladly ignore the fact, that weather, etc. can be considered common, yet many flights cross the atlantic safely. Why? We can say, pilots try to avoid Thunderstorms. We can say, that the aircraft are certified and should be safe on such trips. We can also say there are many options to avoid such events.
About Coffin corner aviation: We can speak about Coffin Corner aviation for many pages, and about how various systems on the aircraft can determine what speed is safe, and how various factors like any "obstacle" under the aircraft (terrain, CB, traffic) can influence what can be safe, but it isn't that simple as you want to portray it.