I think this should be doable with two main steps, using htaccess and overriding the request function.
Step 1: create an override plugin that overrides the function qa_q_request (from qa-base.php). You'll want mostly the same function but for the last line put
return $title . '-' . (int) $questionid;
Step 2: update your htaccess to handle the new format of URLs. Above the last RewriteRule I think you'll want something like this:
RewriteRule ^([^/]+)-([0-9]+)$ index.php?qa-rewrite=$2/$1&%{QUERY_STRING} [L]
Not sure if that's exactly right but should be similar.