I have to say, I love the idea of burning the zombie hordes. Bolts with HEAT damage FTW (esp. since you may inadvertently set the whole fort ablaze).
Also, there's one thing I love about the BABYSNATCHER tag that has not been separated from the actual baby-snatching behavior: Ambushes. At least I'm pretty sure that's related to that tag, since kobolds don't do it (they have AMBUSHER or whatever, so they send groups of bowmen instead of sieging). While stealth zombies seems pretty retarded, an ambush doesn't prevent caravans from entering the map. Sieges do.
I think it'll be interesting to see how a zombie civ might be balanced for world gen in the next version. It'd be very easy for them to conquer the world every time. I suppose one solution would be to set the max number of zombie civs to 1, so the sheer number of other civs prevents them from destroying everything.
While I agree with the clutter worries, I think bones and skulls are pretty much a necessity for zombies (and skeletons, too, though until Toady adds a [SKELETON] tag for creatures, we have to add [NOSMELLYROT] to skellies and wait for them to decay into bones). Besides, where else will you get your zombie-slaying ammunition if you can't use their bones?
[ May 22, 2008: Message edited by: Earthquake Damage ]