I think it would be good if zombie attacks on base were more common, but I don't think scripting them fits with the whole meta game aspect of the zomboid. Instead, would it be possible to have a system similar to how herds work in the walking dead comics, where if one zombie walks past a door and brushes it another will mistake that for an attempt to get in, and start bashing away, causing more and zombies to do the same? This way you could have hords sweeping through neighborhoods smashing down all the doors, maybe depositing some zombies in houses to catch you unawares.
