My thinking was basically to use an algorithm like this:

    if sys.argv[1].startswith('-'):
        company, _, tag = sys.argv[1][1:].rpartition('\')
        if company:
            # look for Tag under Company
        else:
            # look for tag under PythonCore, then other companies

We'd need special handling for Python versions before 3.5 (because of the "-32" change), and possibly for the "-64" suffix as well. But in general, for unique tags you should only have to specify the tag, and the company is used to disambiguate/filter if desired.

SysVersion/SysArchitecture/Version are purely informational according to the PEP (and certainly by intent, if the wording happens to be unclear).