IMHO for the long term, the best would be to have a structure for pre-Py_Initialize configuration, maybe _PyCoreConfig, and pass it to functions that can be called before Py_Initialize().

For example, I'm working on a variant of Py_GetPath() which accepts a _PyCoreConfig to be able to pass the value of the PYTHONPATH environment variable.

That's a more complex solution, so I proposed to first revert, to have more time to design the "correct API".