I'm a gardener – but I don't grow cannabis or magic musrooms.
I have a lathe and milling machines – but I don't make guns (or ammunition cases).
I'm chemist – but I don't make hallucinogenic drugs.
I'm a chemist – but I don't make explosives.
I have both a car and a lorry – but I don't go round mowing down pedestrians.
If I were to have guns, I would not go around shooting people.
I could go out and find a source of prohibited drugs and become a pusher – but I don't.
I have potential house breaking tools around (jemmy bars, glass cutters, bolt ctoppers, gloves, etc) – but I don't go breaking into other people's homes (or raiding their sheds, even).
Just some of the 'possibilities' that I choose not to follow. Not even considered, except as an example list here. I expect there are millions out there who might fall into one, or more, of the above categories. Millions are honest, but there is a small minority who 'break the rules of society'. Clearly that minority cannot be easily persuaded to conform to normal social rules, often for some sad reasons, but more often for other reasons. That minority will never be reduced to zero. If there were no non-conformists there would be no need for a police force.
But we need a police force, and other agencies to help keep us safe from those minorities. Even armed forces to deter international interference.
This is just one case of possible cheating the rules, that needs to be proved – but he will never be a registered firearms dealer again as he will most likely be convicted of having an over-powered air rifle in his possession. That is the fall-back charge, as I see it. So there is a risk that the other charges cannot be proven (even if he did all that has been made public) because he has covered his tracks.
I doubt he has ever been a model engineer, so this thread is mostly irrelevant, if answering the topic title.