We have just designed the Worlds thinnest LED wall light.  25mm thick!  We did it using Tridonic replaceable LED boards and remote Tridonic LED drivers.  Using a thick aluminium back plate and running the board at a low current we were able to keep the LEDs running at the correct temperatures.  These are going into passenger lifts where space is at a premium.  Front disc simply screws on and off to change the finish of the product or service the LEDs should you ever need to.  Very sustainable!