I have seen them too. And books on how to build them from back in the 70s. (what took Tesla so long??)

The completely integrated electrical system that is in most cars today has its advantages and disadvantages.

You really want to have regenerative brakes. It is the only thing that makes an electric care more efficient than a gas one. (that, and it doesn't use any energy when an ICE would be there idling) And this requires a lot more electronics and a processor.

Diagnostics is nice, and that requires some communications features.

If you want slide / skid sensing, it really helps if you have camera inputs and revs and torque on each wheel.

But, when you Microsloth all that stuff (leave it open to hacking) then it is just one big attack point. Further, to the owner, it is a black box, and this is where it is really wrong.