I have done a version of this as part of a move from one EC2 instance to a larger one, but with the caveat that the new server I was using was going to have the exact same base OS image, hostname, installed software, and IP address as the old one. After moving /var/discourse to the new box, I ran a launcher rebuild app and the site came right up.
So under those very specific circumstances, it worked great the one time I tried it.