Right now, envoys can only be used by assigning them to city-states. My idea: allow players to choose between assigning an envoy to a city-state or assigning them to a major civ. This could give the player more to do with envoys so that they are not just the automatic strategy that they are now. It makes sense. Why can't you send envoys to facilitate diplomacy with other major civs? Each envoy could give you a boost in diplomatic favorability with the other civ and give you a bonus of something like extra culture or extra science or a free luxury resource. It would also be nice to be able expel foreign envoys when you want to punish that civ without going to war.