The RAF has been going from QNH to QFE and back again for years....
RPS is a pretty useless concept these days, I agree.
It used to amuse me that the Brize CTR has a top level of 3500 ft QNH - yet the RAF flies on QFE and changes to 1013 at 3000ft - even when TA is different. Pointed the error of this out to the Benson ATC folk, whose airspace is under the LTMA and who should therefore obesrve the associated TA and London QNH - not sure if they've changed anything though.