Found a trailer online for this mode on gmod and became super excited.
From that brief video, all I can say is this mode is going to be epic fun o: Can't wait! Maybe it could be a Halloween treat along with Horror Hill as a package
It immediately reminded me of "Alien Swarm" (correct me if I am wrong). The game-play concept for these type of games are simple in nature with its point and click, but really addictive. I think Starcraft 2 had a similar custom mini-game as well, I enjoyed each version, and no doubt that this version will be just as good.
Hoping to see a wave survival mode, and a sort of "adventure" mode :3