I am not aware of a zero reading being possible at both thresholds- it's beyond my training and understanding of this zero reading, which is faked anyway.
For flight recorder reasons, we have instructions- we should be stabilised in all respects at 1000'. We must be stabilised by 500'. Otherwise you will get phone calls when the flight recorder shops you- as you will if you don't detune the ILS (full scale deflection will get you a phone call). So it is no longer really a practically acceptable procedure- you have to detune the ILS, which you say you need for the GA. Hearing how busy and congested the tower frequency can be, it has become a recipe for an accident these days. That Airbus Captain will have had a phone call about doing that.