I would think the paper charts would be vital. Suppose you lost the FMS, but had some of the radios including a VOR/DME, or some other combination of failures. How could you navigate without the charts and the nav information contained in them? Stand-by instruments alone wouldn't be enough if you didn't have some means of navigation.
Having some voice communication would allow you to be radar vectored I suppose, but other combinations of failures might not allow this. I suppose a chase plane could also be sent after you and then it could guide you to a landing field. I think only certain improbable failure scenarios would create a need for the charts, but it would be very nice to have them in the event of such a scenario.