I know this was already suggested, but this is the main reason remote starters were invented.
If you have a manual, you tie it into the e brake as a safety feature. The ceramic heater would kill your battery quite quickly and that is going to be, by far, the most ample power supply you'll have. A remote power supply/reservoir and solar charger are not going to cut it.
I'll humor you and say this was built and working, then you have the safety of a ceramic heater in an upholstered automobile. The reason your vehicle has 2 or 3 strips of steel in between the engine compartment (where your current heat for your car is generated) and the interior of the car is for safety, there is a reason it is called a firewall.
If you have a manual, you tie it into the e brake as a safety feature. The ceramic heater would kill your battery quite quickly and that is going to be, by far, the most ample power supply you'll have. A remote power supply/reservoir and solar charger are not going to cut it.
I'll humor you and say this was built and working, then you have the safety of a ceramic heater in an upholstered automobile. The reason your vehicle has 2 or 3 strips of steel in between the engine compartment (where your current heat for your car is generated) and the interior of the car is for safety, there is a reason it is called a firewall.