Just a quick note: if anyone needs this sort of thing, I've made a thin electron wrapper around Bitsy so you can download and run it as a native desktop app. Currently I have Windows and Mac builds available, I'll do a Linux build when I install Linux on some sensible machine.
Anyway, here it is: https://github.com/matzieq/bitsy-desktop
You can download builds for different platforms under "releases".
It's MIT licensed, like bitsy, so hack away to your heart's content.
And also - I would appreciate if someone told me if I'm wasting my time and nobody would actually use it :D (well, I'd use it, so I guess it's not a total waste).