Does any airline have provisions for ferry flights? That is do you carry an extra crew member so that the cockpit crew are able to comply with the EASA recommendation in case they should need to go to the lavs?
Just checked my OMA, which does not include the 2 person on the flightdeck rule. However the Interim Procedure Leaflet to that effect is still in force and does not have an excemption for ferry flights. So yes, we should better not take off without an extra crew member or take an empty bottle for "physiolical needs" into the flight deck...