I am aware that some commercial operations could require two pilots. Honestly, is anyone aware of a commercial IFR operation permitted in an SEP type aircraft? Short of citing a real world example, I thing this is a stretch of thinking to a non existent scenario....
AFAIK commercial operations is not permitted IFR SEP in EASAland, but I positively know that i.e. local German regulations require a 2-crew for
private D-reg IFR SEP, in case the aircraft is not equipped with a 2-axis autopilot and altitude hold.