> As a particularly relevant example, we currently have 3 different "warnoptions" fields: the private-to-main one for reading the command line settings, the "wchar_t *" list in the core config, and the "PyObject *" list object in the main interpreter config (which is also the one aliased as sys.warnoptions).

This issue has been fixed in bpo-36763 with the implementation of the PEP 587. PyConfig.warnoptions is now an unified list of warnings options. Moreover, the priority of warnings options is now defined at:
https://www.python.org/dev/peps/pep-0587/#priority-and-rules