Rather than making a whole new model for everything, they could go the Skyrim route. Almost all biological creatures in Skyrim can become zombies just by adding some glowing blue particles. In D:OS2 it should be pretty similar, so they would just have to add some black/dark purple particles and add zombie to the name. Also, making it so that some things can't be targeted is very easy, as it just takes a bool (maybe even in a super class) that is true or false based on whether the corpse could be used for zombies.
I'm actually more concerned over people who turn into piles of ash, because having to make sure not to kill with fire (etc) damage would be a pretty big downside.
In regards to your ability, it could have some bonuses such as shorter cooldown, maybe even be able to target through walls. It would make it a pretty good lifesaving measure.
Perhaps they could also add a spell with a massive cooldown that adds the comeback kid effect for a few turns.
