Single Pilot
In the Citation Ultra, Primus 1000, you don't worry about the right seat copilot display, as it displays exactly what's on the PIC/Left side.
Case in point, I moved the Jim Hendrix, intermittant flickering of the captain's PFD to the right side, to save the company $20k for a new display. Now it flickers on the right side, not in front of me.
Between the PFD and the MFD, there is a ton of info, plenty of redundancy, and should the PFD go out, I can display that info on the MFD, or the right side PFD..
As far as copilot duties...single pilot there are none...
While these days it might seem standard that a plane is flown in a crew, we all started out flying by ourselves...and just because it's a jet doesn't mean you 'need' a copilot.