Perhaps the silliest argument about whether to increase the GST is that it is a regressive tax. Does this mean you only increase or have progressive taxes? The best indirect tax is a GST. A country must have an indirect tax. Overall the GST should be broadened with compensation for low income earners or those on welfare.
It isn't whether an individual tax is progressive or regressive but whether the TAX SYSTEM is progressive.
I doubt many people would argue the more money you make the more taxes you should pay. As it is overall the Australian taxation is progressive however equity is only one concept you take into account. Efficiency is another one.
The Henry taxation review was pretty good and one only need adopt most of its reconsiderations.
In essence you get rid of most state taxes and have broad based taxes in their stead.
Go do it!