I figured before I bought parts and hacked away I would see if anyone has tried something like this.
I have been thinking about how to increase the license plate bulb output. Trying multiple LED bulb options I have yet to be impressed with the output. You can get a bright bulb but the direction and coverage can leave something to be desired. We are limited by the size of the opening, depth, bulb angle and 194 adapter, but there is a lot of space in the bulb housing.
Idea: buy a 15 or 18 LED light array and a spare set of bulb housings, separate the lens from the housing, insert and mount the array run the wiring out the back and attach to the adapter.
What am I missing?

So far the only issue is how much GM wants for the bulb housing (call it $50 each). Maybe a scrap yard would let them go cheaper. If anyone has a connection I am all ears.

Since I am sure this will come up in the discussion I understand this is not everyone's taste but I think LEDs that don't produce ample coverage look too "aftermarket". I am looking for something that would give better coverage and look more factory like the BMW/Lexus offerings.

This is the only picture I can find of the current setup

One of the options I found on ebay