[jessaustin]

Good point, but devices don't have to be able to sense broadcasts on a channel in order to avoid using that channel. Alternatively, the WISP WAP could just continuously broadcast (on known safe channels, as a part of the normal SSID etc. beacon) the list of currently safe channels, as configured and maintained by WISP personnel, and consumer devices could simply not transmit until they received the list.

Even if we were limited to listen-before-talk, the linked study recommended 10 W rather than 4 W, and that was in the urban context of Baltimore-DC, rather than out here in the hills where we rural people would like a choice in ISPs.