Very useful Tecumseh. I realise these things are very complex, and there is often a chicken-and-egg situation.
If PUS, PAC, HCDC, etc. take no action when advised of "illegal" activity, then they de facto condone it. The VSOs would not be doing the job their political masters want if they did not then continue said activity (I am walking on eggs here). Indeed, they may have commenced said activity precisely because their masters wanted it.
Alternatively, the VSOs may be acting for all the wrong reasons, and the politicians/civil service have no effective means of arguing with the 'experts'. And they've tried recruiting retired VSOs to play 'gamekeeper', but those retired VSOs are still 'poaching'.
My feeling is that the buck stops where the power is, and that's why I blame the politicians/senior civil servants.
Can I clarify your opinion? Are you saying the VSOs could fix it by doing proper Requirement Scrutiny?
I think it could be fixed by Ministers / DE&S exercising their legal duties, theoretically, except I do not think either are capable of this. As you say, they are being informed of what is going on, but are not taking action.
I did not write to my MP about Defence when I PVR'ed. I did write several times to my MP about the mess education was becoming, as he was a former teacher in my subject so I thought he would understand. To my final letter before emigrating, where I summarised what I though were the problems, and the potential solutions which I thought the current system was (sadly) incapable of implementing, his reply was "I agree. (it's) Madness. Good luck in Canada". This appears to be an admission of an insoluble problem.