I think the absolutely-endless-world-flooding reanimation is a bit silly to be honest. I mean, how many times do you have to hack an animated corpse down before, you know, it starts to lose limbs and flesh and bits just through you bashing it? I *do* think corpses should reanimate infinitely in evil biomes - but only until you hit it enough so that it falls apart anyway.
This solves not only the problem of: 1) "Wouldn't it be awesome to have corpses reanimate...?!?" but also: 2) "Oh but yuk, then you
have to implement zombie butchery or corpse burning or have to have strange dispelling rituals or otherwise have endless hordes or..."
On living enemies you have to make a killing blow but, since they're already dead, you can't do that to the undead. Maybe you just have to land a certain number of 'critical hits' before it'll fall over? And each time it gets up it would have more yellow and red bits until it collapses through abuse. It should still have all the part and limb requirements of any other creature/dwarf/adventurer (minus nerves, blood, organs, etc): say it loses both legs, it can't walk; it loses its arms? can't manipulate stuff, etc etc.
On the subject of of religion and using ritual to prevent zombified dwarfs: bah! That's not the way to do it. Sure, maybe implement ritualised burial in Fortress Mode, but don't have zombification hinge upon it.
If you embark in an evil biome, presumably this 'evil' permeates the whole landscape. If you have a corpse, no matter where, even if it's in a coffin, then it *will* eventually reanimate. Now, in Fortress Mode, the coffins are all new and flash and sturdy. No zombie dwarf is escaping that. Where you should encounter them is in Adventurer Mode (or even reclaiming a fortress). There, when you come back, the buildings are crumbling and items are strewn everywhere, so then some of the coffins will just have to be worn or broken. Then some of the zombies will escape! Maybe the ones with arms can then let their buddies out too. You get my drift.