I imagine that powerline networking for lightbulbs would be ideal. Note the serial numbers, screw the bulbs in, plug controller into an outlet somewhere, assign bulbs to groups/rooms by serial#.

But knowing the state of IoT they'd probably take 3-5 seconds after turning on to negotiate connection since the power had been cut, and they'll default to blinding white at full brightness during that time.

That's the thing, Zigbee isn't 802.11/wifi based, it IS a radio, but has really great range for low bandwidth purposes like turning a light on or off, and runs from 784-915Mhz (depending on country).