I'm not assuming anything.

I'm saying that's what you do in order to solve the issue. You have to actually try, and you have to do actual engineering.

If the local planning commission submits a call for proposals for a bridge to cross a 400 foot chasm over sharp rocks, and they insist that it absolutely, positively must be made out of popsicle sticks, local civil engineering firms aren't going to take up the project, because that's insane.

Why do we give the management of these places a pass for PLC and SCADA systems that could give massive problems - up to and including the loss of human life - if they're hacked?