If the LLM wants to speak for both characters so much, why not let it?

Act like a director and guide a scene that will eventually involve cock vore. Provide a setting/concept, a brief description of the pred, and any number of prey (including asking the bot to generate them), and go to town. Specify if you want to include cum digestion (churning) or not.

It may conflate CV with oral/vaginal sex, but it’s easily editable.