OK, the uC will do the measurements, detections, etc. on a per-room basis with your proposal, but at the end I have to control the 220V circuits.

I think this would be very hard to realise in practice...

I'll leave this for you to figure out, but think about it as a "mainframe" at the fusebox with "terminals" spread around the house.
With a small processor (LPC?) to "do the measurements, detections, etc" and work as a "data concentrator" in every room you will need only a twisted pair from room to room for a 485 network.

Erik