I'm not condoning the practice of GPS let-downs HOWEVER, the current ground based instrument approach procedures are based on systems that were invented and certified decades ago. (It's not that long ago that we did DECCA approaches IMC in non-coupled dinosaur helicopters!).
Corperate twins now have duplex three/four axis coupled autopilots, multiple GPSs with terrain database (some have DGPS), TCAS, (some have weather radar and GPWS), NDBs, VORs, DMEs and more.
It may not be legal to fly below MSA when IMC (I'm not sure?), however, the laws and procedures are based on ancient equipment and aren't necessarily appropriate today. But like anything in aviation, the laws always seem to get more restrictive, and rarely less so (the 1000ft rule and training from non-licensed sites are notably refreshing exceptions) despite technological advances.
Should there be a case for allowing non-precision approaches to 'points in space' with suitably equipped helicopters?