ICAO isn't a theory
That's exactly what it is.
ICAO airspace management Docs/SARPs are not a theory, to a greater or (in the AU case) lesser degree they are standards used worldwide.
That's exactly what they are.
ICAO set the
theory behind how to develop an airspace concept. Using ICAO
guidelines you are free to, and encouraged to, come up with your own airspace model.
ICAO do not have an airspace model. They do have a Doc on Airspace Planning Methodology (Doc9689) and a Global ATM concept document (Doc9854). I will ask again. What is the ICAO Doc/Annex, whatever, where they describe the airspace model?
I do hope that you all, or at least some of you, understand that, in the ICAO scheme of things, the "separation assurance standards" is the same for all classes of airspace, and as traffic increases, airspace classification and associated CNS/ATM services are varied (increased) to maintain the standard. Put another way, airspace category is related to traffic levels and a fixed collision risk probability, not different levels of "safety" in different classes of airspace.
In which Doc/Annex is this defined? In actual fact, I think you will find that this is untrue.
In one of the documents mentioned above, there is a chapter titled "Application of Risk Analysis to Airspace Planning in Australia"...you may wish to read it.
Outside of your airline career, have you extensive experience flying within the US system?
Alpha