I live in a desert so I dont really need to pre heat shit, seriously I can just not drive it for the two weeks its under fifty. There are prebuilt modules that can control charging rate, they aint fancy but theyre becoming common in my area due to hobbyists. As for temperature id probably just slap a couple electric thermometers to it and call it a day. Worst case for the temp I rip up the back seat and jam an abomination of a heat sink into it.

Frankly speaking id probably just start copying old 1980s and 1970s electric car design.

Anyways I have clearly not thought it through massively, just got the basics down. And most of my opinions come from the place of loathing new cars, they all suck. I drive a 91 cherokee, I know how to work on mechanical shit not electric. But I have messed with enough old electronics to know there is always a workaround, even if it is ass backwards and is a massive fire hazard.