Pilots cannot be expected to jumpseat prior to duty or after duty for that matter,however short the sector.After any incident/accident,the first thing that any investigator will ask is:"Were the flightcrew properly licenced and rested to conduct this flight?"THe notion of pilot fatigue and its proven effect in previous airliner crashes has made all conscientious regulatory authorities take a zero tolerance attitude towards any infringement of these regulations.If an unscrupulous airline plays fast and lose with these regulations,not only is it compromising the position of its flightcrew,but it is openly inviting accusations of gross misconduct.
I appreciate that the off-loading of passengers to make way for crew is a highly embarassing option for an airline but compromising safety is somewhat more than an embarassment.Knowing that they had positioning crew on the flight,who was the bright spark that sold the seats?Was it an oversight(reflects badly on Ryanair's organization)or were they sold to make an extra buck(misguided greed).Either one is inexcusable,but the former is at least forgiveable.
Preparation for a flight is important to any pilot.That hour or two prior to operating is crucial.Accident investigators know this.