Trouble is, those enhanced/synthetic vision systems are OK for aiming at several thousand feet of runway with no obstacles where the transition from instrument/synthetic flight just involves flaring to land ahead but in a helo manoeuvring to a rig?
You still have the problem of going to visual flying to complete the landing which is why NVG are the better option - do you want to be looking in at the screen when you need to be looking outside?
Setting a minimum illumination level (the Met office already provide the data for this) and specifying a minimum generation of NVG tubes would go a long way to standardising things for the purposes of certification.