Hello,
Possibly I have it suggested once when was plying 3,5 years ago. Don't remember and I see its still not implemented.
Idea is to allow players to share vision with other players. Many games becomes just boring when You are very strong and opponent is not even able to scout how strong You are. So in some cases, it will be nice if You can share Your vision with opponent, so he will be able to look around and surrender.