Better still, actually put people with limited mobility in group 1 or group 2 seats so that they don't need to walk so far down the aisle.

Do it strictly by zones, and keep the overhead bins locked shut until the relevant zone is called.

One more bullet point, Cathay business class lounges are also open to Cathay Silver members travelling on Cathay flights.

Looks like a good option for smaller international operators that want to run a frequent flight to/from one city fed by domestic connections (and don't have the volume to serve four or five capitals daily).  Compared to the slow torture of domestic-international transfer at SYD this would be...

Simple, let people with no carry-on luggage board in the first group so they don’t get stuck waiting in the aisle while those who brought giant rollaboards try to jostle them in to the overhead bins.