You have to move past the private pilot mentality here. Please read the governing legislation for commercial operations, specifically CAO82.0 and 82.1 and their head of power, section 28 of the Civil Aviation Act. In commercial operations the OPERATOR is responsible for the competency of the staff, if the pilot can’t flight plan, can’t complete a weight and balance correctly, it’s the fault of the operator for not ensuring he can. If the pilot can’t do it he/she cannot not be rostered to fly. The operator must have suitable systems in place to ensure a pilot isn’t rostered to fly without a current medical, a weight and balance system that allows him to calculate it, and training and checks to ensure he can. A pilot flying without a current medical does not absolve the operator in any way because the chief pilot is responsible for tracking it, it’s one of the duties detailed in CAO 82.0. That’s the reason why certain types of operations require an approved check and training organisation, to ensure this is done to an even higher standard. An operator can be absolved IF there are suitable systems, training, programs in place, and has records to show the pilot was trained to use them and competency was checked.