TURBINE lets start with the top line...."as long as the guy is safe".......and that is what matters i dont give a damm about the so called SOP,s as most i have seen have been folklore that have bee cobbeld together over the years.......how meny times have i seen a PPL holder scrub the tyres in a very tight turn to get the A/C exactly into wind for the run up and yet on the CofA airtest it is recomended that this is done crosswind if conditions are OK (ie not a taildrager in a strong wind)
Or to take your example of running out of fuel if you ask the average club member about leaning the engine most say "not below 3000 ft" and it seems to be some sort of SOP in the local flying clubs,they can only get it from the instructors but its not in the Piper flight manual.
It is infact something that has been passed down from the days of the tiger moth or some such vintage trainer and will leave you 20% short of fuel if you dont lean IAW the flight manual.
As for two PPL,s flying together the aircraft is single pilot so the person in the right seat is a passenger and should not interfear with the flying of the aircraft.
You comments remined me of a conversation i overherd between two young instructors.....a strong wind had changed direction across the two runways and a pilot landed his aircraft into wind on a part of the airfield that was used normaly by gliders as the landing was directly into wind the laning run was short and uneventfull.....one of the instructors remarks to the other that the landing was ilegal because it had not been made on a licenced surface,........i can only think that it would be ok to rip the landing gear off on a licenced surface.