For the contracts that require two crew, I suggest that what they really want is a second set of eyes and possibly to cover the case where the PIC becomes incapacitated.
I would not allow the guy in the right hand seat to take off or land as that would degrade safety.
Your company sops, will or at least should have the pilot monitoring, (the guy in the right seat) role.
Things like calling sustained errors in speed, altitude, tracking etc. Assisting with radio, briefing pax, but a low time, I assume endorsed pilot, flying leg for leg in a single pilot aircraft is not increasing safety.
Are the guys in the right seat being paid the same as the guys in the left?