Re: Interesting justification.
That's what "block heaters" ("Standheizung", in Germany) are for.
Too bad they're only around €1000 or so to get put in.
Except for diesels, where most of the kit is already installed (oh, the irony)...
Just remembered, another problem with idling in winter, with the heater on, is the possible influx of Carbon Monoxide into the passenger part of the car. That can get ugly, fast...