Everyone loved the quick pace and bloody close quarters feel of the game, it's a nice escape from the mechanized world of 5th Edition. People got to bring things that wouldn't normally hit the table, notice the Avatar? He's quite spiffy for this, ignoring melta and flamers. The addition of the doors made a big difference, with AV13 it was entirely possible to get yourself locked into a room. Worse still is if you were locked in a room with an entry point, you were a rat trapped in the maze waiting to be eaten (my girlfriend took that literally and decided to add some mouse toys for the pictures).
We played with basically all the optional rules, the Enemy Unknown was too much work, and the Cold Void was only used if added through the catastrophic damage table. The way we see it, the game is meant to be played with everything, and flavoured by the choice of the Catastrophic Damage table you use, Buried Alive for ground bases, and Void Ships & Stations for space hulk type battles. The one house rule we added was to modify the 10 man unit limit. It seemed to hamper those swarm armies that we'd want to see in the halls, like Orks and Tyranids. So we allowed squads of any size allowable by the codex, however any squad of 12 or more models in the movement phase counted as moving through difficult terrain to represent the close quarters shuffling of so many bodies moving through hallways. It seemed to work perfectly, allowing someone unfamiliar with the house rule to play with little issues, 10 man squad + 2 HQ ICs. Only some small issues for armies that can get multiple ICs per HQ slot, or ICs from non-HQ slots.
As you can see there are quite a few more walls, some blast doors, and a few pieces of terrain on square bases to fit into the system nicely. To begin with I simply made 3 sets of 3 doors in a 2", 3" and 4" width. The blast doors were just some more particle board consisting of a 1" thick base for a 3" tall door to sit on with just some carpenters glue to hold them on. They are the most likely thing to break, but they are also pretty quick and easy to fix.
The only thing I may add is some sort of edge marker, because as you can see some of the edges didn't have walls along the whole edge. This is partly because of lack of extra straight length walls, and part because the ones that did get placed would get knocked off. So something in a similar size to the blast doors, just a simple flat marker representation.
So the overall decree is everyone loves the Zone Mortalis games and we'll probably finish off the club dates playing it. If you get a chance definitely setup something as walls, even if it's just masking tape on the table, you'll enjoy it I'm sure.