nstead mount tiny cameras in their place feeding back to small screens on each pillar.

It is easier to get an immediate sense of spatial awareneess with physical mirrors rather than relaying camera images to a centrally located screen. A camera lens can be obscured by dirt and become useless. An electrical fault woud lead to the driver becoming blind. There's no technical difficulty in incorporating your suggested set-up.

or anything else that you think should be on cars now that isn't?

Freewheel device. Yes, it is controversial-and it has been done before. The fact remains that it is the mechanically the most simple and elegant way of improving fuel economy without hampering performance. Try riding a 'fixie' pushbike and you'll quickly see how useful a freewheel is!