Actually I have seen a setup that was quite close to this. Two separate networks, one of them was completely isolated from another, didn’t have Internet access

Actually I have seen a setup that was quite close to this. Two separate networks, one of them was completely isolated from another, didn’t have Internet access and used a separate set of network equipment. On top of that, the building itself had two entrances - one for the boss and another one for the personnel. You physically couldn’t get from one part of the building to another. It didn’t help the boss though - he was blown up in his car one day. Fun times.