Just read British Light Tanks 1927-45 Mk I-VI (New Vanguard) and was interested to see that the War Office was deliberately spreading tank production around industry to provide them experience in building armoured vehicles as part of gearing them up for the coming war.
Also of interest was the Australian order for 10 Mk VIA in 1937 that, along with 4 older Vickers Mediums (a total of 14 tanks pre war), were run into the ground as training platforms upon mobilisation. This meant there were no tanks available for deployment with the 2nd AIF and they were totally reliant on what was available in theatre upon arrival i.e. obsolete Mk IIBs provided to 6 Divisions Cavalry Regiment to supplement their Carriers (they later obtained captured Italian tanks as per the photo Greg posted on page 1 of this topic).
Last, there was a prototype Mk VI tank destroyer with a 2pdr in an open topped turret from 1935, that was extensively field tested by the 9th Lancers through 1938. The type was rejected for service but it is not known why, possibly doctrinal reasons, however the reliability of the platform combined with a gun that was actually superior to the light anti tank guns used by other nations early in the war.
Now to work these facts into the thread.
With war on the horizon the decision is made to not only gear up British industry for the production of tanks but also industry within the dominions, as such Australia's Mk VI light tanks were locally manufactured and the versions selected was the 2 Pdr tank destroyer as well as the VIC but with M-1919 and M-2 Browning MGs instead of BESAs (maybe .303" versions of the Browning).
This means the 2nd AIF Divisional Cavalry Regiments can be deployed with tanks rather than having to wait for the UK to supply them (if things worked out the Dominions could actually supply the UK allowing them to develop and deploy new designs sooner). The obvious initial TOE would include a mix of light tanks and tank destroyers in addition to the usual carriers within the Divisional Cavalry Regiments, plus possibly separate / independent light tank and tank destroyer regiments.
As Australia always intended to follow the UKs lead on the employment of armour it is perfectly reasonable to assume that Australia would form a separate Armoured Corps, including a Tank Regiment with a number of battalions operating both infantry tanks and light tanks, as well as mechanising Cavalry with light and cruiser tanks. The obvious vehicles would be the Mk VI Light Tanks ( and tank destroyers)and the Matilda II for the RAAC and RATR while the cruiser tanks would be more problematical but I think an interesting option would either be an enlarged light tank or a license produced LT vz 38 with 2 Pdr tank gun.