Quoka
you say
. Class E cannot be provided in airspace where a FLOW control service is being provided.
This is simply not true. The US do it daily! Are you suggesting that the US cannot provide ATC services in class E simply because some aircraft are subject to flow control?
Having flown into Chicago and other busy US airports which are often subject to flow control, the class E from FL180 down to A080 never proved to be a problem even when we were under flow control.
Perhaps instead of looking to Australia for a solution, why not look to those that have done all this before? The US.