How do you remote access an air-gapped workstation? Seems like you'd need to be constantly switching whether your laptop is on the internet-connected network or the isolated network. If the laptop can switch between them automatically, wouldn't that make it possible for an attacker to jump the gap?

Even just having hosts that are sometimes internet connected and sometimes on the airgap network will greatly weaken the isolation. Stuxnet could cross an airgap with just static media, allowing thousands of computers that sometimes connect to the internet across the airgap seems like a fatal weakness.