The QDF is aimed at hot/current topics right ? So while it might be important for a news site or a celebrity gossip site I don't think it will be relevant for every site.
You have mentioned that the client has proposed to build the site with "all the pages you hope to rank for", which means the topic is restrictive and there is a limit to what you can write about the subject. But then to launch the site with this approach you need to get all the content ready and that might take some time.
A much more sensible approach would be to launch the site with a reasonable amount of content and then add the rest of the content when possible. This way you can start with the link building, social sharing process early.
I don't think just because you launch a site with lots of fresh content it will give you a jump start in traffic, but I'm interested to see if anyone had success with this method.