I also ran across a film clip the testing of Ford's M1918 tank, from when the US Army was trying to field its own armour in World War I. While the M1918 never saw action - field tests in Europe found the tank lacking - it gave me a clearer idea of what the armoured infantry does in /Mecha Academy/. In the film footage, it looked like the M1918 was meant to accompany infantry during a charge, travelling with the larger landships of the war while carrying a heavy machinegun instead of anti-armour/anti-emplacement weapons.
In Mecha Academy, I have three types of infantry. Mechanized infantry is more-or-less like today, the boots on the ground. Powered infantry wear powered armour, along the lines of Traveller's Battle Dress, but not quite as sturdy. Powered armour started as heavily armoured space suits for hostile environment then were improved to add extras to let the soldier inside carry heavier weapons for longer times. Armoured infantry essentially drives walking suits of powered armour that gives infantry units more offenseive power to take on heavier targets while still keeping the advantages of infantry, like going where heavier units like tanks can't.
The M1918 tank in the film clip showed me what the armoured infantry is - a level of force that can keep up with regular infantry while still capable of bloodying the heavier units on the field. Like tanks, armoured infantry shouldn't act alone, but sometimes, the situation calls for something outside the guide book. And that's how I get inspiration at times, by finding random tidbits.