Post WWII Australia was quite committed to building new and further developing existing strategic capabilities deemed necessary from war experience, both for defence but even more importantly for economic development.
In this situation it is quite conceivable that a local tank production capability could have been determined to be critical to national defence, in particular if the proposed armoured force, of no less than fifteen tank regiments in one regular and two reserve brigades, was adopted.
The Sentinel program had proven that Australia was capable of designing and building tanks, even with extremely limited resources available during the war, a post war industry would have been a much simpler, less urgent undertaking. At the time there was also limited foreign exchange and the Centurion was very expensive, as well as being considered by some (incorrectly as it turns out) too large and heavy for operations in South East Asia and the Pacific. A perfectly good enough medium tank designed to equip an army that never expected to have to fight the latest and greatest Soviet designs without the support of great and powerful allies, better armed and protected than the M-4, smaller, lighter, more mobile and cheaper (to buy and own) than the Centurion, more reliable and durable than previous British designs as well as the not so successful M-26/46.
In this situation it is not so much of a stretch to imagine Australia developing and producing an evolved Comet as much to build a strategically desired industrial capability, as to boost the capability for the army. It would use common automotive components, suspension tracks etc. perhaps even the same turret and main armament but a modified / modernised hull constructed from newly developed armour production infrastructure. The main visual difference would be a sloped nose and rearranged drivers position with periscopes, swivelling hatch and height adjustable seat. A 20pdr would be nice but difficult and the 77mm HV would do until the T54/55 series was identified in the late 50s.
Such a vehicle would progressively replace all of the WWII vintage and hopelessly obsolete Matilda IIs and Grants in the Militia / CMF as well as the not much better Churchills equipping the new regular army. A full fifteen regiments, plus additional vehicles for training and strategic reserves, exports to NZ and other suitable customers (Israel?) would easily see about 1000 basic tanks being built, perhaps in multiple batches / improved marks, through the 50s.
A series of upgrades could be undertaken in the 60s and 70s, maybe even the 80s for reserve vehicles, giving all sort of fun configuration options. Vietnam, Six Day War, Yom Kippur, even Lebanon in 82 with Blazer RA, perhaps an extreme version in Desert Shield / Storm. New drive train, turbo diesel (MTU V10?) new gun, 105mm L7 probably too big, how about a 76/62 similar to what South Africa did with the Rooicat, or a 75mm ARES or even the 60mm HV gun? Starts with Browning M1919, ends up with MAG58 and Browning M-2. Could be evolved and retained as a cavalry tank with the latest surveillance systems in addition to updated optics and fire controls.
Thinking a Revell (Matchbox) 1/76 kitbash and if it looks good try a Bronco 1/35.