Richmond needs a long 18/36 runway to be viable and CATIIIC ILS or GLS (once proven) as there must be over 10 times as many fog days as YSSY. But agreed, it is by far the logical and only place for a second airport within the basin. High speed rail to YSSY and Central.
Could be justified and acceptable with closure of YSBK to aviation and moving GA to YSRI.