Leady,
As much as I respect your views and experience, the NAS 2b Safety Case was 'implementation-based,' not 'system-based.'
This has been argued to death in respect of 2b.
The transposition of the American model to Australia did not fit a 'like for like' argument in respect of radar coverage, frequency access, sector size, controllers 'per-capita,' etc, etc. It was just not 'like for like' as regards fundamental ICAO requirements when it comes to importing another system and relying solely on an 'Implementation Safety Case.'
Given the glaring anomalies, a 'System Safety Case' should have been mandatory to comply with your beloved ICAO SARPS.
The 'Implementation Safety Case' was an attempted short-cut that did not take account of inherent system differences. It was nothing more than an attempt to 'pull the wool' and ram through a flawed agenda when a few zealots thought they had the political momentum.
Had a 'System Safety Case' been done, you'd have got a lot further old fruit!