I'd rather see this as a specific creature. One of the things I don't like about making skeletons and zombies templates is that a zombie created from a 1st level commoner is the same as one created from a 100th level wizard.
Fast healing isn't generally limited, so maybe fast healing 15 and vulnerability (+50% damage) to acid, fire, and force effects. We can list the special vulnerability to holy water separately.
Mmm, ok, if we're using standard fast healing, I'd say cut it to fast healing 10. Holy water usually does 2d4 pts of damage to undead. Let's make these 50% more vulnerable to that too.