I understand what you are saying but as ATCOs all we can do is to apply nationally or internationally recognised standards. The procedures for VORTEX and other separations are clearly defined and we apply them rigidly. If a pilot asks for more room behind a heavy we accommodate him but, as has been said elsewhere, if everyone asked for an extra minute here or an extra mile there the whole place would grind to a halt.
Different pilots have different views on VORTEX - some want extra time whilst others are happy to dispense with the rules completely. Having experienced an airliner go into almost a 90 degree bank on final approach and an exec jet go completely out of control ten miles behind a "heavy" I never cut the corners on VORTEX separations. I assume that the standards we apply have been deemed "safe" although with several instances recently of pilots asking for greater spacing behind 757s I wonder who decides the standards we apply?
Lastly, I experienced a new one yesterday - 737 in the LAM hold was being knocked around by a heavy jet 1000 ft above him... yet our VORTEX rules do not apply when a/c are separated by the standard 1000 ft.