vilas, you should reconsider your use of the phrase 'dangerous stall characteristics', and implication that stall avoidance is the design objective of STS.
There are significant differences between the requirements for aircraft aerodynamic and flight handling characteristics when approaching and at stall, and for crew awareness when approaching a stall; e.g. provide the pilot with cues of approaching a stall with stick force.
Or alternatively and unrelated, reducing workload with auto trim in some situations.
The effect of STS failure will depend on the objective of STS; poor awareness might be tolerated for low exposure, low risk situations, but if used to alleviate weak aerodynamic characteristics or control effects, not so acceptable.