Hi D6,
Your observations are very valid and your skepticism is well founded. Even a veteran captain would have his reservations flying in a sophisticated piece of machinery with a very young and inexperienced co-pilot.
It could be worked out, however, by putting an experienced co-pilot on the jumpseat to act as safety pilot. So until the new f/o reaches the required minimum time, say 500 hrs, and prior to his release for actual line flying, he will always be accompanied by an experienced f/o in all his flights.
I have seen that many times, and I hope it will work that way for these aspiring wannabes.