The question is....do we want to lose the lower level in the stacks [occassionally] or do we want to screw the higher sectors in the most dense and complex airspace over London? Don't forget the massive increase in R/T loading......and that's even before SRG have written a complete chapter on transmission and readback protocol.
People's jobs depend on perceived work output....this is one result......but believe me when I say that the R/T loading alone should kill this off.