You could do it so that it creates a new monster when it dies, an encounter perhaps to add talk. And you could clean up any blood or mess left.
Of course, I'm thinking in BoE terms, because…*sniff*…I use a PC. Anyway, that's the simple way to do it. You'd have to lower it's max health, though.
EDIT: Well, if it's one monster, it ought to be easy, just by using a constant for the health. If it's multiple types, however, that would require a more complex system, like the one you're talking about.