Yeah. I know it's possible to have a backward-compatible network over regular residential wiring, I have a pair of those ethernet ports that plug into standard outlets, but there would need to be a broadly accepted networking standard for devices that have that feature built in.

Maybe a starting point would be an open hardware, open software server device that connects to the electrical grid and the regular ethernet (via cable or wireless) that manages all the active devices on the power network. If a device implements a protocol the hub recognizes, it registers the device and makes it available for management via a web interface. I think I'd want some kind of manual confirmation before new devices start communicating with the ethernet anyway, as well as a way to grant and revoke internet privileges for devices on the fly, e.g. I might want to upgrade the firmware on one appliance to fix a bug, then close it off again until the next update. There could be switches / dimmers etc. that implement the standard and act as passthroughs for legacy devices to give them a bit of centralized control too.

If it gets good enough for hobbyist / diy electronics makers to start baking the standard into their devices, it could become a defacto open standard. I think it would be cool to have networked devices that won't brick once the manufacturer goes bust / decides to shut down the servers that make the hardware work. I think that should be the bare minimum we demand from hardware manufacturers: that they don't build implicit or explicit killswitches into the devices the sell. But that's a separate ramble and I feel I've gone on long enough here 🙃