Great idea! Adding a huge time delay + disable chatting + game room option might be all that's needed to have this added without risking abuse from the community. People already give away others positions while playing already, I don't see this causing any addition risk than what's already present.
I don't see those limitations being judged as harsh. I think the point of a spectate mode is for those who simply just want to watch. Spectating should be just that, spectating!