There’s 2 problems with this. Firstly, this idea can’t be done with the current spotting system, because when you have one zombie on you , you also probably have another few. Secondly, the zombies in Cataclysm are the running, 28 days later types, and not the big, shambling horde that Romero uses. Unless you wanted a zombie running at you, moaning loudly and probably call the others, you would have to sneak up within one tile.
Not to say this idea wouldn’t be a good implementation for a game in which these problems were nullified, it’s just the game doesn’t fit in with it, although it may become doable in the future if things change.