I would think that being unable to use mercenaries in conversation would cut a decent amount of usefulness out of them - BG3 is designed around group play, afterall. Forbid them from entering conversations and you can’t use them to do anything other then fight, even if it’s stuff like breaking door’s to the Inn on fire.
But why would you ever use mercenaries for multiplayer in BG3, when you can instead create 4 Tavs at the beginning of the game or have other players just play as the Origins?
Mercenaries very much seem like something only useful for singleplayer, when you don't like the Origin companions and/or they get killed off, and you also didn't do the workaround at the beginning of the game to start with a custom party of 4.
