I'm mostly talking about the engine, chassis and transmission section. Whether the whole entertainment or "lifestyle" sections are superfluous or not doesn't event matter, as this really doesn't increase maintenance costs or makes the car itself that more complex. That's pretty orthogonal to the basic design. You could revamp a Model T with DVD players if you'd want to. I'm not saying that we need all that all that added stuff (AC, sound etc), but that even the essential components nowadays require a high level of complexity.

To get a reasonable amount of safety, you have to be either very cleve or apply huge amounts of brute force, i.e. build a friggin tank. Which probably still won't be as safe as other vehicles, neither for the car itself nor the one it hits. And the fuel economy will be utterly atrocious, especially if you want to keep the engine simple and user-maintainable.

I'd like to be proven wrong, but I think that it's simplicity, safety, performance – pick two. Maybe not even that, depending on current laws, standards and morals. I doubt that even something like the VW Beetle or the Citroen 2CV would be feasible today. You'd either end up with a gas-guzzling tank or a not-quite-car like the Vespa Ape, if simplicity is a constraint.

Again, I'd like to be proven wrong. Then at least I know what car to buy next.