In OTL, the establishment of new colonies in Australia ceased around the mid-19th Century: New South Wales, Western Australia and Tasmania were each started individually and then South Australia, Victoria and Queensland were each carved out of New South Wales. There were numerous other proposals for new colonies but they were all suppressed or avoided through deal-making by the administrations of the existing colonies.
So, what if more were successful? Like Princeland being formed out of parts of VIC and SA, or Riverina or Illawarra or the New England region splitting from NSW, or Queensland being divided into two or three separate colonies, etc.
So, what if more were successful? Like Princeland being formed out of parts of VIC and SA, or Riverina or Illawarra or the New England region splitting from NSW, or Queensland being divided into two or three separate colonies, etc.