The biggest problem I can see with a deliberate stall in a PFL situation relates to flying the picture.
I have always been taught to fly pfls with an aiming point remaining fixed in the windscreen. Ie. moving down is an overshoot and moving up an undershoot. Keep it in the same spot and thats where you are going.
In a stall you have a completely different desent profile from that of a normal approach and thus the picture will look radically different. IMHO this would make deciding the point to recover from a stall very difficult and particularly dangerous. Further to this, aircraft that are benign in the stall, tend to sit and wallow at a very high nose up attitude, removing virtually all forward view, making the recovery decision even harder and committing the ultimate sin of not keeping sight of your target field.
Just my thoughts,
Obs cop