I don't actually see a problem with that. My point is, any army which is not prepared for battle should not survive.
I like the idea of having to choose which regions to travel through in order to accumulate the most food. I would suggest this be included in the army treasury somehow. But not simply by having the Sponsor buy the food directly.
Perhaps the sponsor can choose how the food is collected, the rate at which it is payed for as it passes a region.
This food issue may also be able to discourage blob army mentality. If a region can only support so many troops, some will starve.
