I like the idea of the Raspberry PI evoking memories of the BBC Model B computers. Brandy BASIC has been mentioned before.
I built a barebones Linux environment using buildroot with only busybox and Brandy BASIC. I then configured the system to boot straight into Brandy BASIC.
As I don't have a Raspberry PI yet
I'm running the environment under Qemu
Here is a little video of me trying a few things out...
(edited a couple times while I got used to the forum code)