QF2,
As always I stand to be corrected but I believe the question revolves around the higher requirements for CHTR, the downgrading to NVFR is a furphy. The answer has nothing to do with the requirements for NVFR as the flight is still a charter flight.
Therefore in answering the question you have to decide what navigation aids are required so that the charter flight can be conducted to an airfield without an alternative being required with at least one of the sectors being flown under IFR.