Dashboard / Controls
You might want to ignore the existing dashboard altogether and go with a table-based solution. This will give you the flexibility to add a license-plate mounted camera on the front or rear of the car. The rear-facing camera becomes the backup camera, the front-facing camera could be used for precision parking, or just recorded for viewing later.
If you want to get one to play around with, try to get one with a touchscreen, GPS, wifi, and bluetooth. You should be able to get an unlimited data sim from Google Fi, but this is not confirmed.
If the tablet is android, it should be able to run custom software to interface with the vehicle's new CAN bus, reading wheel speed, motor rpm, and controlling the e-brake and motor direction (aka gear, forward, reverse, park). I'm in the process of acquiring one to get familiar with it, see what it takes to write software for it, and connect to the CAN bus. I'll post updates as I achieve these goals.
This is the one that seems to have the most potential (wifi, but no internet, must be connected to phone, which must be hotspot):
https://www.alibaba.com/product-detail/Portable-Wireless-10-26-inch-Touch_1600642954427.html
This one is pretty badass, too: https://www.alibaba.com/product-detail/4G-GPS-Wifi-1080P-4ch-8ch_1600519278890.html
Like