Running Plex media server for Mac as root?

I want to set-up Plex Media-server for my sister-in law on her mac.

They share one computer between a number of kids. There's no way of knowing what user will be logged in at any time.

Can I set up MS for mac to work something like media-server for Linux, spesifically I want it automatically start when the computer boots up (regardless of who is logged in). I want it to run as root (or whatever the OSX equivalent of root is) so that it can read files from any user's directory.

Can this be done?