One idea I heard of a few years ago was upgrading Dubbo airport to international status. Not that it would be used for passengers so much but for all the freight especially fresh produce flown to Asia that currently needs to fight its way into Sydney. Doing so would relieve quite a bit of pressure on Sydney airport along with the curfew reductions you mention.
I don't know if it is indeed feasible to upgrade Dubbo etc but with the current opaque decision making process and appeasing the loudest and most persistent whingers and looking after hidden interests (OK,another conspiracy theory lol) we'd never know.
