Actually, what I was asking for is much more than simply adding another expected Answer to the edit form. I would like the new Combined question type to retain (optionally, as an advanced feature, as you suggest) all the current features of Short Answer, pmatch, preg and regexp questions. That is to say, it should be possible - for each question of those types - to enter as many extra Answer fields as needed and as many specific feedback fields associated to each Answer field.
That is to say I would like those "open-ended" question types to work in Combined the way that Short Answer (and, with my hack, regexp) questions work currently in the Cloze/embedded question type. The only difference being that the specific feedback messages associated with each answer, instead of appearing on mouse hover, would get displayed at the bottom of the whole Combined question text.
No longer being able to display feedback upon mouse hovering is - for me - a regression, but I accept the need to be "politically correct" for accessibility reasons - plus the fact that mouses are not used on tablets & smartphones. The proposed display of specific feedback messages right at the bottom of the Combined question text means that, especially for longish question texts, those feedback messages might be displayed significantly far away from the sub-question "blank" they refer to, which causes a real ergonomic problem. I suggest that this ergonomic problem be alleviated at the time of displaying the question analysis, with marks, feedback, etc; e.g. by printing (small?) numbers next to each sub-question, referring to the same numbered feedback messages at the bottom of the screen. Something like footnotes in books. Those numbers could even be made into links, linking both ways to the footnotes and back. See attached screenshot #1.