You can use a third party camera with your codec. We use vaddio cameras to our SX 80 codecs. The USB output then comes off of the Camera Control Unit.

If you have CMR enabled on the WebEx the SX 20 should be able to call in to the meeting no problem just dial the video address.

The question is how the users will operate this system. Pro quality HDMI switches have gotten cheaper atlona and kramer are making some nice stuff. The question is how will control the system, control processors and programming are still a bit pricey...