Requiring the communication medium to be the same for everyone during a meeting is a great idea. However, I don't this conference call method is scalable for phone conversations. I can't imagine 15 person conference call would be very effective.

I think for larger meetings this "level playing field" solution would probably work much better for video conferencing or combined text/audio conversations such as on Skype. This way simple cues such as "I've got something to say when you are finished" can be used without interrupting.