I think the most important thing for this new procedure to work is that the staff MUST enforce the new concept by checking the BPs - directing the people with different status/class of travel to the relevant line. Most of the time I found both HKG and outport staff not really checking the BPs carefully.

Actually an interesting point I've recently realised is that CX can try and adopt the US/AA way of boarding - print the boarding Group (Priority, 1, 2, 3 etc.). This way it is crystal clear which group should be boarding when without any ambiguities