Good post, accurrate info.
Back in the day... we used to leave our secondary O2 sensors outside of the exhaust flow, with a cap over the end. As in, sitting in the engine bay with easy access.
NO CEL, seemed to work fine.
Another option was to make a secondary O2 sensor simulator, we had to make our own but now you can buy them. A quick google search pulled up the below:
Defcon Products : Oxygen Sensor Simulators
-Steve