Have you not Creamie, really put your finger on the actual problem here. There are tso standards that all owners must abide by in order that an aircraft can be used in an ICAO compliant airspace.
The issue is, as you say:
approved by CASA for your aircraft?
This is the real problem we all have - this takes our aircraft to become orphaned in terms of re-sale.
Approved by casa does not cut much ice in terms of a sale into the US environment.
Rollon US-FAR's for all