Simple...have the system confined
in the CRC. In other words mic and speaker in crew rest facility. The most difficult part of this project would be the signal processing but it's do able (and has been done in other applications...). I'll let airbus figure out the rest. Got the sytsem blocks in my head right now but that's airbus's job. Not mine
PS In my system set up, cabin crew members and pax would not be affected.