I like the idea, but using a cthulhu rules set might be best, as they might have better rules for things like possession.
Also sanity/insanity should play a heavy part in the mechanics.
Plus the general hoards of undead rules used in most zpoc systems doesn't really fit with the show's narrative, which normally involves only 1 or so possessed being in play at any one time.
Still I'm a big fan of the show, so will be keeping an eye on this thread to see what you come up with