By the sounds of things he is a very accomplished engineer who could have earned a good living for himself legally. Assuming that they have some sort of workshop at the prison then it will be very interesting to see what he turns his hands to.
So why do you suppose people do such things then? This chap like the one who converted imitation weapons is a highly skilled artisan who could earn good wages in a well respected trade in the community, but they and many like them end up, quite rightly, serving long prison sentences.
Their obvious talents are wasted in prison surely we can thing of something better to do with them, preferably something that would be a benefit to society but still be a punishment and a deterrent.