Specifically, the Board managed to answer my question in the same way they review games - case-by-case. This is where I believe the system itself is flawed, because in their arguments against classifying Left 4 Dead 2 they cite many things that you are currently able to do in other games, specifically Dead Rising, which encourages the use of creative melee weapons to dismember and kill the undead. The Samurai sword, as the best example, offering equal amounts of locational damage also showing off zombie insides; a game quite easily marked with an MA 15+ upon submission. And that is but one example.
The problem here then is there's no such thing as precedent. In the Board's eyes, despite releasing both Left 4 Dead and Dead Rising as MA 15+ games (among many, many others), they hold no ground to how they should treat Left 4 Dead 2, which is why it's entirely fine to walk into an airport in Modern Warfare 2, kill innocent people and watch piles of bodies build up on the floor around you, but it's not okay to smack a zombie in the face with a frying pan.
Perhaps we should be reviewing the review methods of the Classification Board instead of wasting our time with the futile task of changing South Australian Attorney General Michael Atkinson's mind on an R 18+ rating for videogames.