The POH specifies the aircraft can be operated two crew, our company ops manual requires a co-pilot, CAR's say I can operate as a co-pilot, CAO48 etc requires me to log it as flight-time (though my company prohibits me from doing this).
The POH does not specify that two pilots are required, it only states a minimum of one pilot, as with all other pipers. The Pocono or the T1050 may have been different if the design went through as they were slated to be 15+ seats.
There was at least one RPT operation under regular surveilance in southern australia who had two crew operations on PA31. The co-pilot would log co-pilot when PNF and ICUS when PF and competent to do so. This was all audited by CASA and seemed to be not an issue.
The co-pilot does not have to fly the aircraft, they are there to assist the PIC, which may involve control manipulation. Most multi-crew ops now swap sector for sector so the co-pilot can gain hands on experience and build skill, there is no requirement for this to happen.
Frustrating, as I'd have another 300hrs multi otherwise!
Co-pilot time in aircraft less than 10ton would not be regarded very highly by any prospective employer, I would not lose sleep over the loss.