With remote herd keeping etc. removing the need for going home too often, perhaps an addition of random creature mutations, say one of your pigs turning cannibal or the chickens destroying/eating crops could be introduced. And/or one in every n eggs hatches out a freak... Damage could incurred could be slow or fast paced i.e. cannibal pig could either be a pure mass murderer and kill all others quickly or just slowly much through one pig/chicken after another.
OR
Piggy could mutate into werehoggy that on certain nights cause some havoc.
Seems at the moment there are not enough random, or planned, acts of naughty going on to hinder progress. After all some Gods are malevolent, or we wouldn't be squishing grapes, and we can't all run round petting pigs and sharing flowers can we now... Some of us want to strap a chicken on a gassifier just for fun!!!