Lord Valdez,
this has been discussed before. The weapon-mounted lights may require serious changes to the game engine - movable, directional light source, cone of ling (ling? wtf is ling? i meant "light") that tracks with the way soldier turns, plus you need a way to turn it on and off. I will let the devs answer as to how hard that is to code. Maybe the engine has some like that already.
Another vote "con" was due to tactical issues: while a barrel-mounted light is OK for clearing houses, for moving in relatively open area at night it is a nightmare - blinds the user to things outside the cone and givesa away position. Would be great for enemy snipers, I imagine.
