Yeah, I've done a simple one before. It's just a Docker image. And you build off their base images.
The main issue, I think, as you raised on that GitHub issue, would be working with Bluetooth, but I haven't looked into it yet.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I haven't seen it done, but I'd definitely find it interesting. Have you seen anything about how to make add-ons?