My recollection re the HIDs is the same, although somewhere was a reference that unless the factory fitted them, forget it (may have been one of the state-specific legislations I was reading as I cruised through the Austlii databases). My memory tells me that the headlight casing itself must be self-levelling, not the suspension, but the headlight levelling may rely on the suspension (ie mechanical levelling based on the angle between the front and rear of the vehicle).
As for Fat Boys - my understanding is that they are legal, in that they are the right colour and they are assymetrical (the left part of the beam shines higher than the right) which also fits in with Australian Standards and the NSW legislation (which seems to closely follow the national legislation in relation to headlights). I am not sure about the wattage: the local ARB guy said they were one of the few legal upgrades, advising me (at the same time) that the other (more expensive) "Xenon" globes he had on the shelf were NOT legal because of the whiter colour.
I have had Fat Boys in my headlights for around 17,000km of the car's 21,000km life so far. Much nicer low beam, respectable high beam. I did comment to the dealer that I preferred my VT Commodore's headlights when driving on country roads, and after taking out a couple of Navaras for night spins while waiting for mine to arrive, we noticed the inadequate lighting, which is why we put the driving lights on it.
After going through some closed-in forest trails late at night, we decided that the light even on low beam wasn't enough so we went for the Fat Boys. Definitely worth the money and they've lasted quite well so far.
If someone can find legislation that says they're illegal and can point me to it, I'll happily remove them - the last thing I want to do is be breaking the law myself while encouraging others to remain within the rules. If that becomes the case, I'll be getting myself some running lights and directing them downwards and at about 30 degrees out from centre for the forest runs.