Well, depending on how crazy you want the map to be, you could have lots of Spikers and SMGs to make the map very frantic and have the game be...
It seems to me (though I could be wrong) that once you close the door, all the humans could camp the single entrance into the base until running...
I am making a map in Forge that requires stairs to be merged about half way into the floor. I set up guides to try and keep it straight, but no...