Years ago I proposed that, if the AoA signal is lost while stall warning is active, the stall warning should continue until a valid AoA signal indicates that the AoA is less than the stall warning threshold.
However, one needs to be very careful avoid that the cure is worse than the disease. The whole issue is somewhat trivial compared to the need to avoid getting to an AoA of 42,5 degrees in the first place.