Coaching system?

Just thinking about an idea to let people coach their friends by being able to spectate their games in real-time. The coach would only be able to see what the player can see (maybe locked camera as well?). I think it'd be a great idea to let established players help out their newer friends and, of course, enhance the community like Riot always strives for.

I'm also wondering. has this ever been considered/talked about officially?