But I am betting that quite a lot of the electronic components of cars these days are tied to things, my DPF is a great example, that come from safety and environmental regulation. If you pull the ECU out and tricked the motor into running anyway, I am betting your emissions profile will suck massively. Ditto transmission. The rest of my car seems to involve safety features, sensors and cameras mostly.
By the time you reinvent the car to exclude all these things, then make it roadworthy again I reckon you would end up with almost exactly the standard modern car again. Car makers arent putting computers in for funsies.