With the Garmin 530 installations I've seen on 412 and 76, you just keep programing whatever approach you want (NDB, VOR, ILS, RNAV) on the GPS and let it drive the track bar on the HSI to wherever it wants (does a better job of the correct inbound than the pilot). It also tunes the correct ILS frequency into the Nav receiver. Once on final for an ILS you simply switch the OBS source to VOR/LOC and leave the trackbar where it is. The old 530 is only TSO 129 A1, but you still fly RNAV only approaches with it as long as they exist in the database.
Looked at the S92 panel pictures but can't figure out what is meant by "raw data to monitor". You mean like a wet compass?
I see Malaysia and Brunei are a little behind the RNAV curve, but you could certainly file IFR to Singapore (Changi) and fly the RNAV approach with only the Garmin. My take on the TSO 145/6a is that in the US you can file destination and alternate using a single GPS receiver that meets that TSO, but with the older non-WAAS units under 129, either destination or alternate needs at least one ground-based navaid approach.
Nothing but pilot stubborness to keep you from flying any NPA in the GPS database coupled to the FMS, and simply monitoring the underlying navaids. Fixed-wing guys been doing it for years, and I've noticed the helicopter side catching on now too.
Anybody in the GOM flying GPS Approaches with the 92? I doubt if the North Sea or SE Asia is, except as overlays.
Malabo