Your better off ringing the RMS,then listening to a salesman or someone who has had one done in the past. As you are probably aware the rules have changed and depending on who you listen to you get conflicting views.
Most suggest if you get a GVM upgrade you cannot add that to your GCM it only affects your vehicle not the trailer. Others will say your vehicle is unsuitable if you need a GVM upgrade, so go straight to the source and get their advice.

You have already made your case on here that its legal, why keep asking. Just go to the correct nsw government department and ask the question and get them to write it down for you in plain English (yes or no). Maybe just do it anyway and take a punt
cheers
blaze
ps maybe buy a smaller van

This post is not about the legalities  or weights I just want some feedback on suspension upgrades by Lovell's eg ride,quality of components,setting up for loaded and unloaded etc thanks

My understanding of the laws is that you can still get 2nd stage GVM upgrades, but GCM can no longer be upgraded over what the 1st stage manufacturer specifies.