To do this, you need to add the new windows 10 admx files to your policydefinitions folder in C:\Windows.
First off, reset permissions to the policydefinitions folder (properties>security>advanced)… Change the owner from TrustedInstaller to Administrators (tick the box to replace owner on subcontainers and objects:
Press OK and exit properties, then go back into properties>security>advanced. This time double click on administrators and give full control, then tick the box to replace all child object permissions (answer Yes to any warnings):
Download the latest windows 10 build ADMX files (or use this - https://www.microsoft.com/en-us/download/details.aspx?id=56880). Run the installer using the default settings.
Once complete, browse to C:\Program Files(x86)\Microsoft Group Policy\%version%\Policydefinitions. Now copy\cut all the loose files and the en-us folder (there should be 200+), and paste them into C:\Windows\PolicyDefinitions (overwrite all older files). You may have to drag and drop, and teracopy doesn’t seem to work so use explorer.
Once that’s done, fire up group policy, open your printer policy and ENABLE this user setting (User Config>Policies>Administrative Templates>Control Panel>Printers>Turn off Windows default printer management), then set your default printer as you normally would.