Actually, and I was surprised to discover this, the Matilda I had armour protection that was second only to the Matilda II and were only be taken out by the 105mms. Being armed with a .303" Vickers, cramped internal arrangements and mechanical unreliability, made it just better than useless in Europe, but as a cheap, mobile pill box, that was impervious to Japanese fire, operating in direct support of the infantry, it could have made a real difference, especially if operated in conjunction with the Matilda II.
I am not suggesting that these were ideal but rather am looking at what could reasonably have been expected to available and fit with the doctrine of the day. The Matilda I was meant to be available in numbers to directly support the infantry, being impervious to enemy fire and able to close with and take out their support weapons, while providing suppressive fire. Not the best concept for western Europe but would have worked just fine in the plantations in Malaya. Also being cheap and looking like a tank, I could see Australian politicians loving the things and even arranging local production pre-war with the intent of issuing them on a scale of six or eight per infantry battalion as a replacement for the Vickers MMG.
The Matilda II would be much better and was available in the time frame. Having a cast hull and turret it would even be a local production possibility for Australia, but maybe with local expediencies. One thought that comes to mind is the Matildas engine bay was actually quite large and could probably have fit the GM 6046 (originally developed for the proposed US built Matilda II) and GM had facilities in Australia at the time that were producing DH Gypsy Major engines. Then there is the possibility of Australian production of the 2pdr HE round that the developed in the UK but never issued, it would have made perfect sense for Australia.