I just don’t think military armour, which is an endgame item especially in large quantities (so from intact vehicles), should be so readily available.
So I think a distinction between a strong chassis (Normal military Humvees and trucks, etc.) and actual bulletproof legitimate light military armour that you may find on Bradleys and the like.
Then to make it harder to find have it only rarely spawn wrecked vehicles on roads (so you can only get 4 or 5 plates and the rest are grayed out) while the intact ones spawn in hard locations.
A cool location I would like to see added would be overrun checkpoints/field bases: tons of zombies (and I do mean tons, you would need them to overrun a base and the noise/smell of the last stand would have attracted more) and one or two heavy military vehicles: The APCs we have now, Combat modded Humvees, etc.
I also kinda think there might be a way to add tracked vehicles to the game.