Thermal storage needs to be quite large though, at least with the stone/brick like mass they used back then. And you need to isolate it, otherwise you have no control over the release of that stored heat. I wonder if new materials, maybe something that undergoes phase change in that temperature range, could be a lot more space efficient.
I’d rather force safety requirements on all cars. Like limiting blind spots at the front and everywhere else, limiting speeds of vehicles above certain weights, increasing license requirements for vehicles that have higher safety impact etc.