I have often meditated about the subject of #6. However, I'm not clear on whether the Legions or slave labor built the roads. In either case, the labor relations standards were much different. I expect the penalties for failure to meet expectations/standards were a mite more harsh too.
Currently, there's a lot of road work taking place to accommodate things that are supposed to increase the tax base & boost local employment. I'm distinctly unimpressed with what passes for road building. I foresee massive road degradation under the increased traffic due to lack of proper road bed preparation. Which, of course, means the paving contractors will have to come back and suck up more tax money to "repair" their oversights. I'm thinking the Romans did have a better idea there.