I've mentioned before that this already exists. The NSA maintains mirrors of Stack Overflow and Wikipedia that get synchronized from the Internet to classified

I've mentioned before that this already exists. The NSA maintains mirrors of Stack Overflow and Wikipedia that get synchronized from the Internet to classified airgapped networks once every 24 hours. I have no idea what the software is they've used to do it, but you could arguably file a FOIA request or something since the code they're using has no reason to be classified. They've open-sourced simple tools and libraries like this in the past.