I've worked with industrial equipment that creates repeaters that connect to a special Wi-Fi AP. You can string the repeaters along in a tree pattern. Any client near one of the repeaters can connect to it and have access to the network. The repeaters are connected on layer 2, so it's just like making a tree of hubs. The repeaters have intelligence to send the packet to the right place on the tree without broadcasting it to the entire network.
Is there a consumer product that does this?
Is there a way to do this using bridging in openWRT?