I don't know the specifics, but essentially you could take the code from the aforementioned plugin and alter it to convert the comment to a question. The Comment to Answer plugin queries the existing question ID in order to create the answer under the correct question (starts around line 130 in the q2apro-comment-to-answer-page.php file). You'd need the question ID portion to query the database for the last used question ID +1, but there's an inherent risk of doing this simultaneously with someone submitting a new question. I'd also like the plugin to convert answers to questions. Too often users forget the Q&A etiquette of when to post an answer vs a comment vs a new question.