As great Western Sydney Stadium is, $360m is not cheap and unless the conditions are right, it's hard to get that level of investment from the government.
That's why, IMO, simpler Stadium designs should be considered for any additional venues.
@Brian potter's suggestion is a great one, Central Coast Stadium cost $30m to build in 1999, which with inflation would be $56m in current dollars... now I doubt you could rebuild it for that, but still you're looking at around 100m
CBus Stadium's design would be roughly $200m and there are plenty of other more 'boring' designs which would allow fans to enjoy action in a full seated, covered stadium, with modern amenities and can generate a good atmosphere.
Changing colours, award winning designs, steepest elevation for seating which required special certification, multi-tiers etc, are all nice but if they drastically increase the price of a development so it is no longer feasible, aren't necessary. I'm sure the likes of Cronulla, Manly, etc (and their fans), if they could pick up the likes of Central Coast Stadium, CBus or even some of the flat pack UK stadiums and put it where their current venues are, would happily take it.