There is actually already such a system in windows 10 called P2P windows updates, by default your computer can become a "hub" to update computers on your LAN, and also other computers over the internet to unload microsofts servers (you can also setup your own computer to download from microsoft + local PC + internet PC), i have setup one computer that does windows updates in my local network and is set to use P2P only for local computers, and all my others windows 10 computers on my network are set with metered connection (fake metered) so that they seek updates only from Local forbidding them to download from internet.
This is a useless and broken feature. It does not work as intended. I have tried all special methods of changing the metered connection specifications, etc... to no avail.
Machines forced to update only from my laptop; which I update at other locations, but bring home often; never get served an update, and those machines at home that were strictly kept on a separate physical network were disconnected from the internet completely.
Trust me; I have monitored my internet and local traffic under several different configurations.... its not as simple as clicking that magic button. This is Microsoft..... things always work as not perceived. Each new major update; I try to get it to be served by my personal machine to the others; nope; no dice. I have even tried having that laptop connected to the internet, but also connected to that separate network; nope... no updates on the private network.
If you block one update server; there are countless other web aliases that the os can try.... and it will continue to try if there's an internet connection.... endlessly until it finds one.