I like this idea, and it reminds me of a related idea: The inconvenience one has to deal with if one is hidden and is holding a lit candle, lantern etc. and wants to drop it.
When an attempt to drop it is made, one gets this message:
That's not going to stay hidden! You'll need to come out of hiding first if you want to drop that.
Then one has the schlep of having to unhide, drop lantern , and hide again. What I wish for instead is while hiding and holding a lit item to be able to some how toss lantern (for example) in one shot without having to do this three-step.
There still should remain the chance of others seeing you while you do this. I believe that if one is hidden in a room and tried to pick up an object from the floor, creatures in the same room have a chance to notice... I would agree that the same chance should apply when someone chucks a light source off their person.