Can I use an Apple Homepod as a speaker and microphone for WebEx, Skype voice, etc? I spend a lot of time using my Macbook Pro with work-related web conferences. My ideal setup would be a high quality speaker and microphone that I can use via bluetooth/airplay/wifi with my Macbook for the audio portion of these web conferences. Added ++ if there's a physical mute button.

Can the Homepod function in this way?
Unfortunately no. It is not possible to use the HomePod's built-in microphone for recording audio to a Mac. You cannot Bluetooth pair the HomePod to a Mac in order to use it as a combined speaker/microphone either.

Other products exists that does what you're looking for. For example I'm using the Logitech Group speaker/microphone combination for web conferences. However, it is quite a different product from the HomePod.