With regards to:
carrying the same alternate, and that if you are tail-end Charlie, there may not be room for you? Even on the taxiways? I'm surprised how often crews are presumpuous that they will just go to Macau or Shenzhen when they get down to minimums
It may be that I am a little green about the ears, but if my flight plan has been accepted with a particular alternate, then yes, I expect to go there and find room for me.
It is up to each airfield (at the flight planning stage) to say "No, pick another alternate; we have reached our capacity".