In the attached zip there is a cm2 file that may be of some use. It injects slaving code into the currently selected prop or actor so that the prop's yrot channel takes input from the yaw (yOrbit) channel of the main camera.

I think the file fulfils the first three points of your "teapot" scenario. The fourth point seems to imply the rather dubious assumption that two items with the same (or inverse) yRotation will always face each other. In the case of the teapot and camera scenario this may be close enough to the truth that it does not matter. But I suspect that the more complicated case of a laser sword would soon show the fallacy. With a teapot sitting on a table, it's yAxis is always going to be in line with the world yAxis. A sword may be, and usually is, wielded in such a way that it is rotated on all three axes, and its yAxis will rarely be in line with the world yAxis. This means that it may be very far off "looking" at the camera, even when it shares the same yRotation with the camera. So although it does what you asked for in matching the yRotation of the camera, it may not do what you need in some situations. At the moment I have no solution to this more complicated scenario.

Getting back to the attached zip file. I had to add ".TXT" to the end of the name, in order to post it to this forum. You will need to loose the ".TXT" part of the file extension befor you will be able to extract the zip. After that, install it like any other poser content. You will end up with a camera file in the path:

RuntimeLibrariesCameraLesBentleyCURRENT ActorSlaveToYaw.cm2

In Poser select the prop that you want to use, and apply SlaveToYaw file. This should slave the yrot of the prop to the yaw of the Main Camera. There is also a SlaveToYawOff file included to disable the slaving.

It seems to work in PP2012 and P6, so it will probably work in everything in-between.