A Gamemode just like Gmod's Trouble in Terrorist Town. While MM and SMM are like it, they are quite different. What im saying is this Gamemode should have:
-Special equipment menu
-Detectives
-Traitors
-Guns randomly placed around the map
-DNA scanner for detective
-Almost everything in TTT
Sure, some of this would require a client add-on, but that's no hassle- download the client and you can play any TTT server