Well actually they could still be profitable if they moved the vehicle to a different market segment.
So you stop selling the crap exec/omega BS and only sell Calais etc, you are in a different segment so volume is lower but margins are higher.
Yes it would work but GM don't tend to operate that way, they rely on volume.
Even with higher margins, you will never cover costs building a low volume vehicle like that. Regardless of higher margins, lower volume means increased build costs due to lower economies of scale.
Research and development costs alone to keep up with (and compete) in that segment are far too large for a locally made car. BMW, Mercedes etc. have the luxury of worldwide sales to cover those costs, and they still receive funding from the German government.
Why would another manufacturer want to come here?
It costs 4 times more to build a car here than it does in Asia, and double what it does to build a car in Europe. What manufacturer would CHOOSE to double or quadruple their unit costs?
They also receive a lot less funding per capita than other major automotive industries in Europe and the USA. The Australian government gives $18 (US) per capita in funding, compared to $90 per capita in Germany and $96 in the US.
Considerably less funding per capita, much higher unit costs and extremely low volume sales with little to no export potential due to the AUD in arguably the worlds most competitive market.