Forgive my intrusion here as I'm not an instructor:
Surely as an instructor you have a moral obligation and a duty of care to ensure that the person you are signing off is up to standard, how can you tell if they just fly in a straight line for mile on end? When I pay for the professional services of an instructor I want to get my moneys worth (I am Scottish after all!), I would want to demonstrate at the least an EFATO, PFL, stalls in various config's and one or two circuits.