This is nonsensical, Australia has among the worst human rights record in the Western world in regard to immigration policies. Practically every Australian election since 1990 has hinged on immigration on some fashion. Not to mention hugely OP.
Cities in Australia can become very large already given time considering the amount of free tiles available. I'd actually turn all the grass tiles there to plain, actually.
Why should Australia exist though? It's basically a bog-generic Western country without it's own independent history, culture, foreign policy, language or
even it's own flag or head of state. It's rich stable country simply because it's the size of the mainland United States but with 20 million people; with no previous cities, with no borders. How could
any government mess that up?
The English UHV & AI settler maps just need a little tweaking. How can Australia spawn a revolt event from England when the UK gave it local government to save on expenses? What are you supposed to do? Send spies to Indonesia, build improvements & become a vassal or the highest ranked civ?
Its a nice place to live, but I can't think of less deserving Civ gameplay or history wise.