A number of my colleagues having seen this thread unfold, have expressed a view that the understanding of some of the issues would be enhanced with a simple guide (not necessarily referenced based but a personal and historical view) with less emphasis on the Performance Classes for those States in which they are not, necessarily, mandated.
This has been done and it is referenced below in its latest iteration:
The introduction and evolution of Category A procedures - from runways to heliports in city centres
It provides a view of the introduction and evolution of Category A procedures and their progression from the original intent to mirror those of fixed-wing, to their use on small sites and city centres - both at ground level and elevated. It leans heavily on the recent work of the Heliport Design Committee on the ICAO Heliport Manual (ICAO Doc 9261) and goes beyond the contents of the ICAO Performance Manual (ICAO Doc 10110).
Some of the techniques are not yet in use as ICAO Standards but are expected to be in the near future. The more interesting parts - for pilots who follow the development of hospital sites and their required procedures - will be familiar, if only because they reflect the continuing development of Category A supplements for use in HEMS operations - mostly in Europe but also those States for which the risk to third parties (property as well as persons) is mandated in regulations.
As usual, your comments are welcome.