I like the idea!
One thing I am unclear about: is this about making it easy to publish from my laptop/desktop computer or from a running mybinder.org session?
Asking because for the “publish from a BinderHub session” there are a few issues on GitHub discussing ideas and their trade-offs. In particular the problem of “please don’t put any private credentials in your binder”. If that is what you want to target its worth digging through those (I can try and find them).