It would be great to add this feature, so as, we can guide or learn some cool tricks from our friends. When a person wants to spectate his/her friends, he/she should be able to send a request to spectate his/her friend's match from their pov. Now this request should be accepted by the friend for him/her to spectate the match.

Edit1: The spectator should not be allowed to use their mics, however they can use the whisper chat. Also tthe spectator should only be able to spectate his/her friend (not the whole team).