>> Has anyone done it this way and what would be the benefits over straight domain move via 301 + domain change in WMT?
I have experience with that. I moved servers to an IP formerly hosting several web sites. Since the domains were pointing to my IP, the former URIs were serving up my content since I only had non-www redirects in place. I didn't notice it until a few months after I obtained the new IP addresses. Even though it was over 2 years ago since I implemented the 301s, I still have several thousand reported backlinks from these webpages (reported as url1 via url2) on G WMT so the 6 month rule is not really concrete.
To this day, I still have reports, on and off, that they link to me.