It would be pointless making the navigation equipment totally immune to r.f.: it is required to receive signals to function.
Obviously true, but are you saying that the GPS antenna etc has to be or is usually inside the (Faraday cage like.) fuselage? Afterall most basic GPS units will not work optimally under tree cover, let alone inside an aircraft body - no I have not tried it, that would be operating a superhet radio reciver and against the rules!
I was suggesting that beefing up EMC shielding between the passenger area and avionics (Including wiring looms etc.) might be desirable to enable the use of electronic devices without (or with minimal) safety concerns.