This is done!  Here's how to change default mic states...

The trick is to do this BEFORE your call begins.  Before anyone has dialed into your call, click on the "Conduct Now" button.  You'll see the default mic states.  Simply select the settings you want, and close the window.  Our system will save those settings automatically, and when people dial in to your call, they will have the mics you pre-selected. 

Also, if this is a recurring or reservationless conference, and you have set this up BEFORE the call begun, your settings will be saved for all future calls as well.