could this be done with a mod? I mean not specifically the migration, but maybe to respawn a lot (or even all) Z's near you/on the map. It would be a nice workaround until they handle it in the upcoming updates. I love this game (3 days in) and I restarted a lot of sandbox games because there was too much loot and too few zombies for me, and I had the same "problem" after a few ingame days, even with lower loot spawns and high zombie population. No need to barricade if you wiped out your whole neighbourhood
