You can do this with Chrono's "SetLight" events. They allow you to control whether or not a player is allowed to use their light. Don't confuse it with his "changelight" event, though.
Err, why would that work? This almost completely overwrites the normal light function.
-Toggleable player-source light? Maybe it'd be nice if we could toggle whether or not players emit a light around themselves in addition to the flashlight 'beam' itself, since right now players always emit a light along with the beam.
Actually, due to a bug with the TGE engine, the light around the flashlight is only visible to the host. Should probably state that somewhere - er, well no, since it's not really advertised as a feature anyway.
-Glow FX on the flashlight lens? Might make it seem a bit more obvious where players are when using the flashlight.
I'll see what I can do about it.