I'm sure your well aquainted with the use of Rain-x antifog & a squegee(sp?). I have heard that making a fresh cut in a potato & rubbing the windshield with it works like anti-fog. At least it does on the inside of a helmet visor.
I will second Frank Lee's use of a fleece lap blanket & good boots.
Here is a link to some seat heaters. I'm sure you can find out more specs.
Carbon Fiber Seat Heater by WarmSeats? and Other Jeep Parts and Jeep Accessories by 4 Wheel Drive Hardware-RH2
Is it possible to put defrosting elements onto a windshield yourself?
As for the heater systems, you could make an regulator/rectifier to convert from 110vac to 12(?)vdc. This would alloy you to use the same heating element from the wall or the batteries.
Could you make a heat exchanger to extract heat off of the traction motors & give it to whatever storage system you have, assuming coolant? Only have a pump move this coolant if it is at a certain temp. or temp. difference.
Good luck
Don