I think this should be moved/split off to another thread, but I don’t know how to do that in Discourse. (Does it need an administrator?)
Getting the dependency declarations right – and maintaining them – won’t be easy.
For starters, it turns out we don’t currently have a canonical list of modules in the standard library. (Building Python and looking doesn’t count; you’d need to do it on all platforms/configurations. Docs don’t count either; there are plenty of undocumented internal modules like _socket.)
If you’d like to help with creating such a list, let me know. It would help with PEP 534, which aims to split the stdlib into “mandatory” and “optional” parts. (That could also be a first step toward a more modular stdlib.)