Do you want your Q2A users to comment on your Wordpress posts? If yes, it's a bad idea.
Are you worried that Q2A site and Wordpress site does not have the same design layout? If yes, it's a bad idea.
(By the way, if you want to install one of them on your domain, and the other on a subdomain, it is even a worse idea.)
Another thing to consider is that Wordpress installation have speed problem if you don't enable AMP plugin. We, humans, still see it's loading very fast. But Google is ironically too demanding.