I think Supply units should have to be built alongside military ones! that'll give having these huge armies moving and camping about some real plausibility. The real Legions needed mules loaded with supplies to travel in real life, with groups of men dedicated to gathering wood, water and additional food too. You'd still need to pay the soldiers upkeep fee too, of course. Kind of like having the villagers around in age of empires.
THGBlackScar's comments