If we consider the causality chain, that the STALL is caused by a "lack of sufficient lift", which is caused by the range of the actual "airspeed" and/or "AoA", it may become clear that if we could sense, or measure directly "the lift", and thus the "lack of lift", then that would be perhaps an additional parameter, that would add to the reliability of the STALL detection/calculation mechanism.
I respectfully disagree, and mostly in how you phrased that.
Lack of lift typically results in descent.
What happens at stall is the dramatic change in lift generation due to the disruption of airflow at a critical angle of attack.
Before that, lift and drag are generated in a particular manner.
Beyond that, the manner in which the airflow interacts with the airfoil changes. (More turbulent flow, less laminar ... etc)
If you know your AoA, and your critical AoA, then you know how close you are to a change you'd rather avoid.
To measure lift, just what frame of reference are you going to use?
