Hi, as I think CDDA is potentially THE roguelike for 2013 I want to share my idea.
How about removing the “safe period” before zombies start to spawn in / static spawns - and replace with it totally different starting setup and allow kind-of-grace period with a twist.
My suggestion is that for the first 8 hours there are no zombies, just infected normal people. These people are weak and disoriented but still human - you could barter with them or rob them or try to aid them or even have some sort of missions - and killing these infected people would cause severe morale loss and retaliation from humans. These people would aim to survive, so they start stashing stuff and raiding places, perhaps attacking well supplied people discouraging early heavy looting and barricade their houses, fight invaders and each other occassionally and generally act like civilization is about to fall … as it is. All their attempts are left unfinished because sickness prunes them.
The further the infection progresses more disoriented these people are, they might attack the player but generally be too weak to be challenge - rather something of a nuisance/hinder gathering supplies since you cannot kill them because of morale loss.
After 8 hours people start turning to Z’s. Not all at once, but at course of 48 hours. Disease takes the weak first, so naturally first zombies are weakish (but still major threat to average unprepared sick people) - These zombies attack people and once they die they become Zombies too after being diseased corpse for few hours. At this time frame you could try to for example kill the few early zombies in one area and carry their casualities to building and burn it / otherwise dispose corpses to make urban safe haven, atleast temporarily before walking dead start to swarm, move and try to find the remaining living…
After 56 hours is gone world is totally “zombified” and people - except for some surviving NPC’s - are gone.
This would create awesome “world is literally falling apart around me” start instead of entering empty world. You would meet and interact with the people who later become the horde…