Thanks for this write up, Niall...I was actually getting ready to start work on this very project here
This is particularly useful in my scenario, for a number of reasons. I work for a K-12 school and the AD/network structure is...different, from most places. I do not have access to my WSUS server, AND it sits in the DMZ behind my internet filter (don't get me started). The entity controlling the approved patches for Windows 10 has them on a delayed schedule due to the fact that they test all patches first to make sure that they are compatible in our environment. I have the potential to stand up my own WSUS to use with CM, but the short version is that it isn't happening in the immediate future.
So in short, I needed a way to upgrade all my 1511 stations to 1607 (or even the creators update) in a controlled manner, rather than letting WSUS hand out the updates and simultaneously bottleneck my internet filter. Thank you for your work on this!