Most of the cost of producing a car is in the design, sheetmetal tooling, dies, employee training, etc.--i.e. it's not all from just some circuit boards, knobs,

Most of the cost of producing a car is in the design, sheetmetal tooling, dies, employee training, etc.--i.e. it's not all from just some circuit boards, knobs, and servo motors that drive all the fancy accessories. So a brand new designed and built from scratch hyper minimal car with no accessories would still cost $15k+ and be extremely hard to sell to the public. In reality someone shopping for a car on a budget is just going to buy a few years used instead of cutting out all the accessories in an attempt to scrimp. So the unfortunate truth is that there is no market and no profitability for a purposefully minimal car. The closest you will find are rental market and commercial fleet vehicles like basic sedans (Chevy Malibu), pickup trucks, and vans where the automakers know there is such high demand and guaranteed income that they don't need to pad them with extra frills.