We've had some frustrations with end users shutting down their machines accidentally at end of day, causing updates and software pushes after hours to fail. We wanted users to have the ability to restart, and for administrators to be able to shut down machines if needed. We investigated a few options using group policy and user rights assignment, but both options ultimately did not work out because it removed the ability for the user to restart their machine.
After some research, a recent post in a Citrix forum made a note of a new registry hive that was released with either the 1703 or 1709 build of Windows 10 that allows for way more granularity when it comes to managing the desktop interface. This includes a key specifically for only removing the shutdown option from both the "Shut down" or "Sign out" menu and the Power menu.
The registry hive can be found (or created) under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PolicyManager\current\device\Start