I enjoy NPC interactions when their dialogue change over the course of a game. Events are mentioned, important figures are talked about, sometimes they might ask my character what's news. But beyond that I get that there is limited change in an NPCs discussion/interaction probably because there are more important matters in the game that required more attention.
You've put some thought on a solution though and the 'Sensor Area' is a great idea! Perhaps making a mod for it to be added to other games overtime will allow it to propagate to developers and become commonplace in gaming.
Thank you for sharing your thoughts and ideas! It's interesting how the lack of immersion in a game can feel like a detraction from the whole gaming experience.
RE: Game Dev - NPC's and their dog-like reactions to re-interactions.