sunnywa,
Please don't miss the point; there are a number of safe practices that would be in breach of the 500ft rule such as 'offshore shuttling' and 'HEMS operations' - both of which are currently permitted (conditionally) below 500ft.
En-route let down is an procedure to permit a descent offshore below LSALT (only with RADAR) to VFR before reaching the destination (to avoid a ARA to a complex where there may be many platforms/rigs). It is not an approach procedure per se. If the required cloud ceiling for VFR at night is 1,500ft (currently 1,200ft to permit VFR en-route transit at 1,000ft), it will force an ARA under circumstances where the en-route descent is the safer option. It will also prevent a night VFR inter-rig transit with a cloud base less than 1,500ft.
The OM cannot contain a procedure that is in contravention of the Rules of the Air; in any case, competence for these rules has been taken by the Airspace Agency (not the Aviation Safety Authority) which has resulted in VFR operational limitations being eliminated from EASA OPS - this has removed the basis for OM procedures in compliance with regulations.
Up to now, Operational Regulations have contained the limitations for such operations with appropriate mitigation.
There is no problem with IFR; however, in the North Sea there are IFR route structures which have low level collision avoidance levels (mostly for icing avoidance). These might now be in contravention of the levels contained in the Appendix to the new regulation.
No, none of this is a big deal but the proposed regulation has been drafted by airspace experts who have no operational experience. ICAO Annex 2 (Rules of the Air) is a combination Annex; it was produced well before Annex 6 (Operation of Aircraft) and therefore contains the first attempt at providing SARPs for operations. The distribution of rules between the two Annexes has never been regularised.
Jim