having more than one way to beat an army, like being able to steal supplies or cut an army off from resupply.
an army without food could forage, but would have to do so depending upon the terrain they are in.
If an army gets their supply lines cut in say a desert, they would be in a very bad position, losing men to starvation.
It would make and allow for different regional terrain to matter all the more, since forage might not be so easy to come by.
This would mean supply lines would also have to be defended, so having players invest all their forces in one huge MOB army would have a disadvantage. If the mob loses its food source, it has to go home. Defending supply lines would serve to increase the depth and strategy of a campaign as well.
food for thought