This observation leads me to believe, that the Light aluminum armor should be near invulnerable to everything but their artillery. Sure, it'll be expensive, but that's no real problem for vehicles. Especially since they have to split their drivers over 3 different designs. Note also, that our autocannon has less ammo than their machine guns. If we make armor equal, then it becomes a game of who shoots first, which they will win. If we make it better, then we get an advantage.
Excellent job on the research and I agree with the assumptions. There are a few problems, though no with anything you said, save you saying we should use aluminium.
If we had a 12.7mm MG, we could pierce the enemy's armour with AP easily and actually have a slightly faster reaction time due to the lower weight of ammo. Unfortunately, we have no such thing.
Giving it aluminium wouldn't help unless we gavee it Light Armour. By your own assumptions, a .60 cal would pierce Thin armour of RHA quality at short range. Considering it's the jungle, the fights will mostly be short range. More armour and the use of aluminium would drive the cost to 5 Ore, 6 Ore if we make it entirely aluminium as you suggested. If the car is at all complex (unlikely, since it was only complex for Moskurg due to designing Petrol Engine), it'll be Very Expensive or a National Effort.
There is hope, however. 0 Armour can be reliably penetrated by AP rounds. Our 1910s carry AP rounds. With the gun in the turret and the gun in the passenger seat, we could unload a storm of AP rounds into our enemies with a quicker reaction time. With allowing the turret to be equipped with an autocannon instead, we can have some of the cars be used as medium/long-range support which occasionally happens in the Jungle. It'll be especially useful in the Desert due to the longer ranges and little to no cover. Finally, if we actually manage to develop RHA they won't be able to damage them with anything save that Stallion. They'll have a 0 effective weapon (Brumby) and a 1 effective weapon (Stallion) against us while we have two 0.8 or 0.6 effective weapons against them (1910), totalling their 1 vs our 1.2/1.6. Our weapons are better than the Stallion for anti-infantry too. We win.
While writing this post, I realised that their car was Expensive due to complexity. The managed this despite not having Petrol Engine or Crude Battery technology at the time. I reckon we can be a bit ambitious and have our turret be electric, increasing our reaction time further.
Design the AS-MV21. First priority is getting it equal to the Struunk in terms of armour and vehicle performance. Second priority is making it cheap. Third priority is RHA. Fourth priority is electric turret.Glory to Arstotzka.