Its a good ideea, especially when you spawn as prison warden trainee when you're killed in jail as a squad member...
Well, to begin with, you giving a proper use to the system will not mean that everyone else will.
Secondly, keep in mind that as a squad member you can apply for PC using the external application.
Now about the idea of either troopers, trainees, or even trainee wardens... Keep in mind, if you're in one of those three groups, (except the cases where you spawn as one for whatever reason and it's not your main role, either due to you being part of the criminal world, or just a squad member using that shortcut) it doesn't mean everyone has a proper understanding of it, and knowledge regarding its use. Being in one of those three groups when your intent is to be on the lawful side comes with quite an obvious reason. If you didn't get in a squad when you enjoy enforcing the law its due to either your lack of experience, or your lack of discipline and proper behavior.
Whenever you spawn as PC you are damned to read all sorts of stuff in the team chat, ranging from constant insults between trainees, different languages as well as constant spamming.
Now imagine we give them access to a command which allows them to contact pretty much all of the lawful side of SAES. DE, SAM, Official Squads, PC. Yes, true, they do have access to main chat and also can easily spam it, and often do earning themselves punishments such as kicks, and mutes. Right.
Now lets take a look at the already chaotic radio chatter which is going on. Ranging from relatively new squad members who lack the experience with the radio, but at least attempt to keep a proper use of it, going to squads who do manage to give it a proper use, and still then get unprofessional and pretty much misuse the radio for quite some time, until someone requests them to stop, and eventually they do, freeing the frequency.
Go on, add the trainees to the mix.