IMHO the key to having a safe operation with cadets is the quality of the Captains. The RAAF have had low-time pilots (with varying ability) in the RHS of transport aircraft for years, but there is a high level of formal supervision compared to airlines through the process of flight authorisation (getting an "auth"). This means that the Flight Commander (or "autho") will considers who flies with who on what mission in what conditions.
For example, a Flight Commander worth his salt would not pair a green co-pilot with a below-average Captain to carry out a demanding task. A squadron is small enough to manage that but the problem with an airline is, once a low-time pilot is qualified as an FO, they are paired with any Captain. We all know that amongst airline Captains, there is a diverse range of ability from barely-competent to walk-on-water. An airline Fleet Manager is hardly going to look at todays flight to a demanding destination, check the weather, and decide that Captain Bloggs and FO Newbie is the wrong crew for the conditions. That won't work in a cookie-cutter world.
IMHO, cadets need to be paired with highly-competent "old bolds" for an extended period. That means their line-training period should be more like 1000-1500 hours with an above-average Captain that maintains a reasonably steep gradient to keep the operation safe while bloggs learns the ropes.
BTW, 2 degrees nose-down and idle keeps you out of a lot of trouble in a high-level UA – keep it simple.