In the case of the failure or partial failure at any time of an appointment to fill a vacancy under the terms of this order, including the case where there are fewer applicants for a vacancy to be filled by the appointing body under paragraph (4) of article 6, the Commissioners may fill that vacancy by co-opting as a Commissioner any person whom they consider to be suitable having regard to the provisions of this Order and any person so co-opted shall, in respect of continuance in office, be on the same footing as if that person had been appointed on the appointment date immediately preceding the co-option.