I want to use Python to access MFC document files generically? Can CArchive be used to query a file and view the structure, or does Python, in opening the document, need to know more about the document structure in order to view the contents?
I think that the Python code needs to know the document structure. 
Maybe you should make a python wrapper of your c++ code. 
In this case, I would recommend to use http://sourceforge.net/projects/pycpp/>pycpp which is my opinion a great library for making python extensions in c++.
How To: View MFC Doc File in Python