We are working on a solution now, I unfortunately do not have a solid ETA at the moment. The solution will allow you to upgrade to TH2. What you need to keep in mind is you will be sending 3GB+ to each machine so the issue with bandwidth will still be a factor.
We're looking at getting Windows 10 implemented and I ran into a problem with trying to upgrade an older version of 10 to 1511. What I ended up having to do was get the Win 10 with 1511 iso (over 4GB), copying to the patches folder on the Shavlik server, renaming it to the file that it was trying to use (once it downloaded and failed), and running the install again. For whatever reason, when letting Shavlik try, it wanted to use an 'Education' version of the iso and only downloaded an 85kb file. Once I had the file copied and renamed, running the install did the trick. Make sure to select the correct version of the 'Install Selected Patches' dropdown (1511 for me, but there were 3 available options).
We have a guide on upgrading to 1511 here: Windows 10 Build Upgrade Deployment Support in Patch for Windows Servers
For the most part, the process is what you described. The ISO needs to be downloaded, prepared, and then it can be deployed.