Matt,
Where would you expand Richmond? It's pretty hemmed in - Richmond town to the west, Windsor to the east (at least under the flight path)... and the road and rail would both need to be improved.
Unless it's just an 'overflow' or LCC facility (as Avalon is for Melbourne).
121.5,
For a start, Kansai and Chep Lap Kok are both in reasonably sheltered, relatively shallow waters, not open sea.