Why not Richmond?
As one who operated out of Richmond for more than a decade I can tell you Richmond is not only FOG CENTRAL, but there is absolutely no way of extending 10/28 sufficiently and the provision of a runway of sufficient length oriented E/W would involve sending both road and rail underground if the Rail link and the main road between Windsor and Richmond townships were to be retained.
Add to that the limited infrastructure and the probable need to relocate the RAAF flying operations. The one thing that cannot be engineered to ensure uninterupted operations is the dreaded fog. Anyone who has operated into and out of Richmond will fully understand just what a problem it is.