I don’t think you need to worry about all the permutations. I just did one for each room and then when the light layer is on it is only at 65% opacity so they blend with each other.
Some tweaking was required when borders of two images were maybe too hard… I actually mocked it all up in Gimp first using the layers in there and clicked the light layer on and off to see how it looked. Adjusting the order of the layers I found was important.
Once I was happy I just exported each room. Some room had two images if there was a bedside light and a main bed light. In this case I use an icon to tap on to switch the bedside light and tap the room to switch on the main light.
