I don't think that the A300 is a bad airplane... one DHL survived a SAM attack and was controllable enough to fly on engine power as a sole means of control...to me that says something about that plane...the flight controls aren't designed to take the stress of rapid large flight control oscillations. In the case of the VS the torque moment is tremendous well above certification...
As an aside Vp which is Va based upon stall is Vs*(nlimit)^0.5 but since stall speed increases with weight the actual maneuver speed is not a constant
An accelerated stall above Vp would impart a force that is above the limit load