If you only have one monitor and cannot get a second monitor, the hotkey solution would be this:
1. for each possible face cam location, create its own scene.
2. In Settings->hotkeys, set a hotkey for each of the scene, so you can switch to every scene with its own hotkey.
3. the scenes differ only in the face cam location. To minimize duplication, create a source group and put every source in your primary scene into that group except the face cam.
4. add the group to every scene (with "add existing" option), so you have everything mirrored in every scene except the face cam
5. add a separate instance of the face cam source into each scene (with "add existing" option) and place it where you want it to be. It's independent from the group to enable it to have a different location in every scene.