Slamer,
As I think you know, in FLTCH the airspeed is being controlled by the elevator and the autothrottle will going into hold which is exceeding useful in allowing the pilot to adjust the ROD by repositioning the throttles. There is only a problem if the autopilot is disengaged and the pilot doesn't follow the FD pitch command.
It sounds like you are arguing that a stickshaker is not sufficient to prevent a pilot from stalling an aircraft. That may be true in this accident in SFO and in the DH8D in BUF, but that is a separate matter.
The fact that it is possible to stall the aircraft by misusing flight modes like FLTCH and VS is IMO not a shortcoming of the design as much as a condemnation of the training and licensing system that put that human in the pilot seat.