I agree with the line of thinking that Cadets are not an unsafe option for an airline, provided that the systems are in place to ensure all parties (this includes the crew members sitting beside them in the LHS) are trained appropriately.
I also tend to agree with the line of thinking that most LCC's will utilise Cadets as a means of reducing costs. Whether that be by bonding, reduced wages, kickbacks from training organisations etc.
The problem is appropriate training systems and reducing costs in an airline environment rarely coincide.