Quote Originally Posted by Re Berengario I
Sincerely increasing armor with experience wouldn't make any sense, new armours won't grow out of nothing just because you fought a lot, you need an armourer able to build them and money needeed to buy them.
Looting dead enemy soldier bodies was for the most cases the only way how poor equipped soldiers could gain some armor which they couldn't afford. The references to these events can be found in the medieval chronicles.

Victorious army could be awarded such way. Hussites are good example, because most of them came from peasants.

Of course the question is - is it possible to implement such feature in game. Likely not.