The ravages of war suck. Peasant migration helps, and the region itself will grow faster as population increases. But, really, what more can we do, except add a "Rebuild it all now" button for you to click when your war is over?
Pretty much, something similar to drafting, with morale/control/loyalty/production penalties, where you could could choose to forcibly migrate some peasants to an adjacent region. Maybe a large gold bounty for peasants to relocate.
