There's already the mastermind rogue and whispers bard.Rogue: Propagandist (Think Assassin's Creed meets Thomas Paine)
Now, this is an example of how, in a future edition, multi-class archetypes could be used. Because a propagandist/social engineer archetype could work quite well for rogues or bards alike. But not for 5e. It would have to be built in from the start.