low level airspace that is intended to be the domain of VFR, given most IFR equipped a/c can climb above A100.
This is the only bit I have trouble with. Most IFR aircraft are not pressurised. So most of the 3,000 odd GA IFR aircraft are below 10,000 ft.
And dear Aunty CASA requires specific approval (& airframe log book entry) for oxygen - even portable systems. Bring back a portable system you buy at Oshkosh, use it here and you are illegal.