[dimpase]

> this wouldn't necessarily guarantee that what you import from sagelib will necessarily be available or configured to work with sagelib, unless that piece you've imported has all python dependencies. Is that right?

No, not really - what you can import will be working, whether via python bindings in sagelib, or external ones. The corresponding ongoing challenge of sagelib/sagemath development is to un-vendor a lot of components currently bundled in. Debian has managed this in their own not very portable way.