Both of these ideas were/are thought up of in relation to dark and dimly lit DM matches.
Footstep & crouching sounds: Sounds for footsteps and crouching for whenever a player moves. With the hide-names script and a dark map, it could introduce a new challenge in DMs.
No Lights player-type: With no lights, you're going to have to rely on items and the environment. Items or tools to go along with this would help players see in the dark, such as a match that stays on for maybe 1 minute before being extinguished. Could be a very neat thing to have along with zombies.