As the number of WiFi devices on a network grows congestion issues start to take hold. Devices farther away from the AP may have trouble maintaining a constant connection, and low priority IoT devices can reduce signal quality for things like smart phones and laptop.s
To me, an obvious solution is to use the existing HPAV standard, or a similar, simpler standard, to connect smart devices. In theory, one link near your router (which has to have AC power anyway) could bring a large number of switches and plugs onto the network without adding any wireless congestion.
I'm having trouble finding any devices that use this, but surely I'm not the first one to think of it. I know designing safe circuits to interface with mains voltage is hard, but it's clearly already being done in these products. Does anyone know of devices with this operating principle, or a good reason why it would be infeasible?