I am very happy to inform you that it works!
You can create the necessary WordML fragments in a Drupal theme_preprocess_node function, in order to define a variable that can be added to your template as a {{ twig }} variable. I did, as you suggested, add 'raw' to the twig variable ( {{ twig|raw }} to ensure that the result of the WordML encoding and serializing did not get 'escaped'.
Thank you, once again, for your assistance.