I joined the airline as a cadet, straight out of high school and have loved the experience.
I have no doubts at all that the experience has been a good one and that you have put in the required work to get through the course and become a 320 F/O. Your assertion however that Jetstar cadets have any greater chance or opportunity of moving to mainline than other QF group pilots is wrong. A lot of the early cadets have indeed moved onto a legacy carrier but it hasn't been Qantas. Air NZ are very happy to take Jetstar's cadets off their hand!