>>1. Gasoline-burning heaters instead of electric heaters.
In Northern Europe, many higher-end cars have factory-option fuel-burning heaters to pre-warm the car in the AM. A company called Webasto makes them, but there are probably others. I think there are both diesel and gasoline models, but they’re more common on diesel cars from what I can tell.
http://www.webasto.com/us/markets-products/car/heating-systems-for-automotive-industry/
It looks like they have / are developing aftermarket heaters for electric and hybrid cars. There’s a link at the link that talks about bioethanol heaters, which seems sort of silly. Gasoline or diesel is much more readily available.
The really old Volkswagen Beetles had a gas heater as an accessory too.