I'll ask this question, as it's been someting I've been looking for for quite a while, but have you considered whether BASIC Engine could be adapted to the ESP32 and the FabGL VGA library?
I have ordered an Orange Pi (AU$40) and look forward to running BASIC engine on target hardware, but I like the idea of getting kids to make their own computer that they can then program in a modern version of BASIC. The FabGL hardware is very simple, just needing some leaded passive components to get a working system with VGA, PS/2 mouse and keyboard and simple audio.
There have been other attempts to do this. Eris, by Paul Scott Robson was a good attempt. However it didn't get as advanced as BASIC Engine before Paul moved onto other things, and there was not much uptake by others.
R.T. Russell has also released his BBC BASIC code and it is being ported to the Raspberry Pi Pico, but that does not have VGA output or a framebuffer.
The Colour Maximite 2 has a great version of basic, but the hardware is quite expensive (comparatively) and needs a commercial PCB made.
Given that BASIC Engine has moved on to the H3 platforms, I'm not sure whether this would be seen as a backwards step, but the ESP32 platform is very inexpensive and quite capable, not requiring the extra surface mount video controller to get suitable VGA output.
Anyway, this is just some ideas that I've been considering.