I would have thought that part of the definition already included as a prerequisite to VFR flight at night to have a discernible external visual horizon. (No more than 4/8ths of cloud and VFR conditions).
How much will this little junket cost. A one line addition to definitions perhaps but, irrespective of how many hours of instrument time is required by the NVFR pilot, the aircraft must be instrument equipped, the pilot must be similarly equipped, and rated on the instruments he/she wants to use if you want to fly in non-VFR conditions. Night VFR is not non-visual flight.