Joining mid-conversation would actually make it harder to implement ...
But i think that wanting the game to chceck party in close proximity, open all apropriate tags, and simply swap Protagonist in front of camera, as if they were there this whole time ... would be doable.
Problem starts with Multiplayer, bcs in this way ... it would still be the dialogue initiator, who would have full control ... even (and that would be the problem) over OTHER players characters.
I still dont understand why cant we change Race for our hirelings.

Lets us play Githyanki as racist as they trully are!