Interesting discussion!
p.j.m
Your expansion drawing above looks great except for a couple of issues:-
1. The land to the north of the existing hangers and east-west runway is approx 50ft below the runway surface level [river valley]. Your north-south parallels, and the northern most east-west [in blue north of the existing paved runway] is not buildable!
2. Likewise, your proposed extension to the east of the existing east-west is also a deep land depression [and creek] between the runway and the Windsor township [which is elevated compared to the existing runway]
A single north-south [or parallel set] is technically doable as far south as Blacktown Road, possibly futher south to where you have drawn. The road and rail might link with terminal/s built in the south-east quadrant south of the existing road and rail lines with tunnels under said north-south runways and taxiways.
The land aquisition costs would be astronomical as Richmond/Windsor and surrounds has in recent years become quite popular for townies and small acreage types!
Are the political and financial ducks in a row for such a large and likely locally unpopular project? Who knows! From what I know of the local discussion, it is the usual mix of those that don't like the noise, but like the RAAFie's and Yank's in town spending money. A civilain op would atract the same division I guess.
The only sale to the locals would be a reduced o/fly [Richmond at the western end, and Windsor at the eastern end] footprint from a north south runway!
If the State were to consider a loop line linking the Richmond line south to Penrith, then the locals get another public transport link they would use [Penrith shopping], and the state could loop services in opposite directions through Richmond and Penrith back into the suburbs. There's your airport Pax feed and quick air link for western sydney residents!
CATIII, an ILS to the north-south [built with necessary lighting], you could overcome some of the negatives of the terrain [very high terrain] not that many miles to the west, the terrain south and to a lesser extent to the north is relatively flat.