do you think a number 2 pilot having been copilot might have made a difference on that day,
What of the times when 'junior' spoke up and saved the day? I can think of two in QF that I know of- and they weren't 'minor' issues. What of the times when because of the actions of junior the mistake was averted and it didn't even get to the 'saving the day' status? All this despite the 'experience' that surrounded them that was silent (or didn't notice the mistake) at the time.
You say that 'what if' the F/O in Lockhart River had more experience. What if the operator had a better organisational safety culture? Any deficit in this culture wasn't one that developed as a result of cadets, it was a long standing GA culture.
So how about we start with a more sound premise that avoiding prangs isn't just about experience. Plenty of experienced people prang aircraft every day. Plenty of inexperienced people save the day when those with a few more hours under their belt stay silent.
I didn't start this cadet comparison (again) but I'm stuffed if I'm going to read PPRUNE and read continued examples of poor thought processes and lack of understanding of safety systems to continue.