Except the battery is under the flesh bags in the seats who dislike a 40C ass baking in all but the coldest of conditions.
That's not relevant, heat doesn't remain at the source, not in any example cited, not in an ICE not in a battery pack. Also the fleshbags are not sitting on a battery, they are sitting on a seat, mounted with an airgap above a frame mounted above a battery, and a trivial amount of insulation means they wouldn't see even a single degree of temperature rise in the cabin.
You are inventing problems that have been solved in the most trivial of ways.
Also WTF are you talking about, if it's anything less than sunny outside people pay extra for heating in the cabin, and my heated seat system definitely is higher than 40C. Are you suggesting "coldest of conditions" for someone living in Tropical Australia?