Sorry for the late reply. I absolutely support older navigational stuff. In FSX times I flew the Stratocruiser across the pont using weatherships and celestial navigation (although a bit simplified) and I am quite firm in using the INS.
However I love realism, so I'd either go old school, radio navigation + RNAV, or simulate a panel how it would fly today- with GNS or GTN. If I would update the panel on an aircraft like the Duke with modern avionics, I would certainly through out all the old radios, transponders and outdated stuff like the RNAV unit, which would clean up the panel and save some weight after all.
It would be great if we could opt for a panel without the RNAV unit (and in this case, the copilot's HSI could be used for GPS2 / NAV2).