This is interesting to me. How would the DNS work without touching the internet? Or do you mean to say that only DNS touches the internet and rest of the site would be offline?

If I made some cool security-camera image-recognition project with YOLO and wanted to sell installs to my friends in the area, would I need touch their DNS settings too? Personally: I feel uncomfortable changing settings on other folk's routers. If I could get away with helping them set a static IP without touching anything else, I'd much prefer it.