If I might make a suggestion - I definitely think this would be a valuable addition but I’m cognizant of difficulties converting existing topics to the Q&A format and figuring out what to do with answer comments if converting from Q&A to discussions, which may require a lot of manual work by admin-types and significantly more design/dev work to puzzle out.
One thing I think might be a middle place with a quick solution to start out is making it quick and easy to convert from one format to the other when there are no responses yet - a grace period, of sorts. Imagine the following situation:
AWESOMECOMMUNITY adds the new plugin. USER1 isn’t aware of the feature and their newly-created topic would be a perfect Q&A rather than discussion. ADMIN1 wants to convert but can’t. Even though no one has interacted with the topic, the only way to change the state is to get USER1 to delete and repost as a Q&A.
I could see value in even allowing the poster to make this change in this narrow case - perhaps they started something as a Q&A but by the time they finished their draft, they realized a discussion was more appropriate but forgot to switch the post type back. While they can delete and repost, it’s messy and could be frustrating for them.
I could see other options to avoid this second situation, such as a review phase where the user is reminded which format they’ve chosen and asked to verify it but the Discourse model is so clean and simple, adding more steps to post creation seems like something to avoid.
So, in the interest of addressing the “whoops, crap, I didn’t know/forgot about this new feature” situation, I would encourage making it possible for the OP and Admins to convert between the two post types provided there’s no answers/replies to the post. I leave it up for discussion whether comments on a question should count as “answers/replies” since they seem to be much more easily converted into discussion responses than the other possible interactions in either format.