To your question about scale: have you ever played Elebits? In that game you had a gravity gun that you'd use to lift things and find little creatures. The initial levels were about picking up books and small things on a desk and by the end of the game you were tossing houses around.
Given that, one solution to consider is to work backwards and scale down a bit. Maybe the first level is automating a single object (light bulb). Then a small appliance. Then a single room. THEN the first house?
Starting with a single object also might be a nice introduction to some of the core gameplay elements (linking your assistant, manual off/on, automation, etc.) before upping the complexity.