Keep in mind that most option substitution would be at the file rather than widget level.  The scrollbar switching would be for something like editor windows, which are basically generic.  For the option dialog, we would copy ConfigDialog.py to, say, configuration.py, adjust the imports, and convert to ttk (and pep8, as we wish).  Then use_ttk would be used for choosing which file's ConfigDialog to bind to the Configure IDLE menu item.