" Some of the wording in Terrorism Acts might be a useful starting point where even possibly knowing and not reporting suspicions is an offence [‘light blue touch paper and retire’ moment on my part] "
Now that could be 'challenging' to say the least ! I can see all sorts of issues around 'knowing'. and proof. Certainly encouraging a reporting cultures in areas where there is a clear safety element might be feasible, though I feel the 'authorities' have already shot themselves in the foot with their rather silly campaign to encourage us to shop anyone who we think may be illegally transporting immigrants or drugs. Apart from it being a rather nasty 'shop your neighbour' idea, the folk I saw explaining this showed considerable ignorance of flight aircraft flying and took no interest whatever in real aircraft crime - such as the thefts of Rotax engines from hangars across the country. Clearly not part of their tasks and targets!
So I suspect many pilots would simply ignore all this. Not worth the hassle and aggro.
I entirely agree; some serious forensic accounting would be a great help, in this and many other areas. Far too many dubious activities in the UK are hidden away; I suspect many accountants and auditors are well aware of where the dodge parts are - some useful tactical blindness occurs no doubt !