you wil be pleased to know that the HotPot module already works with TextToys. At least, it works with the TexToys html files.
I haven't come across "Marking" exercises before. It will be interesting to investigate.
You may also be interested to know that I soon intend to begin enhancements to extract information from "Michael Rottmeir" quizzes which are based on Hot Potatoes quizzes.
If you would like to send URLs or examples of non-standard Hot Potatoes quizzes you would like to run via Moodle, I would be very interested to see them. My email address is: gordon at-sign kanazawa hyphen gu dot ac dot jp