From what I read in the forum and support articles, you should already be able to exactly that for more than 1 year.
See " Allow access to Live TV and DVR" in the support article about managing access/restrictions to your server:
Allow access to Live TV and DVR
Members of a Plex Home can be optionally allowed access to tune Live TV that’s been set up or both Live TV and DVR. When enabled, the user will be able to use Live TV in supported apps. If DVR access is also allowed they will only be able to manage their own recordings.
Note : Remember these are available only to members of your Plex Home. Live TV access requires at least Plex Media Server version 1.11.0. DVR Access requires at least Plex Media Server 1.15.4
