I'd Love that feature but I don't have any clue how it would be done.
I think it Is not possible becuase if you've been in big convos before you'd know that when someone adds you your not in the convo until someone says something, so that could be anyone in the convo.
I don't know if that means The person who added you is instracble but that seems pretty convincing to me that you could not do this, then again People used to say you couldn't split the atom.
P.S. If Any of you already wrote this thaught down I'm sorry, I must have missed your Reply.