Darkman, your idea is good but i have in idea, every turn a unit surrender after the number of turn in the territory= the little food the troop find in plunder in that territory. For the ammunition the normal -1. Exemple in a territory with a one ipc value, units in this territory begin surrender 2 turn after the encirclement, one turn for the encirclement phase, and the other for the number on the territory. For a territory with no icp value, unit begin surrender on the first turn after the encirclement.
One unit every turn, the players chosen which unit i surrender.