Have you gone through your Golden Image to remove anything you don’t need, as there is normally an awful lot that can be removed to reduce the size of it without affecting functionality. Often there is a lot of caching of packages by the package manger as well as multiple kernels/modules, man page removal, swap file etc that take up a lot of unnecessary space. A 14GB compressed mender artifact does seems a little on the large size. Once you start auditing your root file system, you will often be surprised as to what’s consuming space that you were unaware of.
There’s a more in-depth discussion below on large image sizes.