Because using the Rift is a very personal experience, I have been thinking of the idea that one person could use the Rift with an xbox controller (for example), while the other person is using the monitor with the mouse and keyboard. That way one person could have an overview of the map, either helping the person in the Rift, or creating obstacles for them. That is just one example I can think of, but the main question is, is it possible to do?
I like the idea, it reminds me of the commercial flight simulators facilities where they have a control room that triggers system failures while the pilot is in the sim.
Some of the pitfalls of this approach (Separating the display, latency etc) would be easily avoided by using two computers networked together, rather than trying to do everything on a single computer.