It suddenly dawned on me that engine block heaters and pluggable hybrids are a match made in heaven. The manufacturer could integrate the block heater right from the factory at a cost of probably less than $5 when spread over the full production run of the vehicle.

You'd plug the car in at night and the block heater could be on a thermostatic switch. This way you can plug the car in hot, like right after pulling in the garage and it will only charge the battery. Then once the coolant drops below, say, 100 degrees, it would kick in the heater too in order to maintain an effective coolant temp. You'd go out the next morning to a fully charged battery, reasonably warm engine and have full electrical assist and the high FE and low emissions that come with having a warm engine.

To be really fancy, I'm sure you could even program in some sort of button on the FOB that's kind of like remote start. Press the button 10 minutes before you leave and the engine heater kicks up to maximum heat and it runs the electric interior heater and seat heaters at max heat from wall current. Then you hop in your vehicle with say, 120 degree coolant temperature and a 70 degree cabin temp. All of that without using any fuel or battery power because it would be plugged in when you hit the button.