MS has seemingly forgotten about the offline user demographic.
Yeah! I miss getting program updates in the mail on 3.5" floppy disks too!!The entire industry has forgotten the offline user!
But what you can do is once you register the Office 2016 and make an account you can go in and there is an option to retrieve the old type of install key and also download an image to create a disc. We retrieve the key and put it on a label with their account info but you can create a disc and change a nominal fee for the media creation and give them it as a set.