If meta is to discuss the community outside of the community, then why Q and A?
Wouldn't http://www.discourse.org/ be better?
When all you have is a hammer...
Plus, Meta isn't just discussion. It's discussion + bug reports + support requests + waffles + feature requests. At least some of that is pretty well-suited for a Q&A site, and what isn't can be kinda shoehorned in without too much trouble.
Discourse looks promising... For discussion. But integrating it would be kind of a hassle, and would do very little to improve the situation for all of the other purposes Meta exists to serve.