Right now, having your factories retreat (instantly) is nothing but a boon for your country.
My wish is that once your factories retreat, all factory supplied objects incur an extra 15 minutes downtime until they return to the front, to simulate extended supply lines, delays in delivery, and the time to retool and move the factories.
You'd STILL be safe (on most maps) from the constant attacks the frontline factories suffer, but you'd have an incentive to try to move them back to the front.