[jarcane]

The RISC OS people have produced a custom ROM that runs only BBC Basic at boot: https://www.riscosopen.org/content/sales/risc-os-pico

There's also some stuff here on the RPi site on other BASIC options: https://www.raspberrypi.org/blog/celebrating-50-years-of-bas...

I would actually love to re-case an RPi in it's own retro keyboard unit and turn it into a proper TV-computer of old. Alas I don't really have anything in the way of that kind of solder/hardware skills.

EDIT: Actually, following some of my own links, it looks like someone's beat me to it: http://www.fuze.co.uk/