If Australia stopped coal exports, we could have a significant impact on the viability of coal as a fuel source. If we're serious about climate change we could halt coal exports immediately, which would spike the cost of coal and lead to the closure of coal plants already on thin margins. Sounds drastic but maybe not if you consider how little time we have to correct course.
We'd need take care of the coal workers. Potentially continue their salaries for a year, then phase it out gradually. There's only $35k workers in the coal industry. Average $100k salary = $3.5 Billion per year. Doable.
I don't know what to do with the coal mines and their investors. I'm inclined to say screw them. Let them go bankrupt. But this might hurt investor confidence in Australia ...