Night Vision Goggles (which could be for either traitors exclusively, or for traitors and detectives) would be a fairly balanced addition to TTT. Maps like the Clue variant/wintermansion/spooky/that Wild West town one (There's four good examples for you, could possibly also be useful on amsterville) with that f***ing light switch would be more interesting as the T's could operate in the darkness, and their improved vision would allow them to assess situations better, while not being so OP as to detract from the inherent requirement of actual skill.

Another suggestion I'm tagging on here is mustard gas and it's respective chemical protection suit, to protect them and/or detectives. Mustard gas could be a realistic choice here because, due to it's density, it tends to settle into low-lying areas. It also causes chemical burns to any flesh it comes in contact with. Thus, my suggestion is that we add it as a re skin of the incendiary grenade, possibly using a tinted form of the smoke clouds from the smoke grenade. Two possibilities are that it could do low levels of damage for a long period of time (3hp/s @1:30 minutes) or that it could be more like the flame grenade in that it does high damage, but disappears quickly (10hp/s @ 30 seconds).
I'd go for the former, mainly because it would be different from the flame nades, and infinitely more annoying. The chemical suit for this could be denoted by a player model that is also tinted. You could argue that this would not help the traitors, and would help point them out to others, but it's a chemical suit, which by my personal experience, people tend to flip the fuck out over.

This thread is titled "NVGs" instead of something about poison gas because I'd really rather see the NVG's get added than the gases, if I had to choose one. Still though, you know you want both.