Theoretically you could calculate if someone will starve with a given army and territory. Every plate gives you 1 income. Every peasant costs 2 upkeep per round. Spearmen cost 6, knights 18 and crusaders 54.

You get the values for your own territory. Eg you know how much you have saved and how much you earn or lose every round. Every territory has its own values. You have to connect territories to combine their savings and income.