After a sudden brain wave last week I had been googling to see if anyone of the mechanical keyboard models had easily modifiable firmware and realized that the very keyboard I was typing on had a removable daughter board… and there was already a ATmega32U2 (note U2 & not U4) replacement controller available for it called the Frosty Flake.
I ordered one of these and will be documenting my changes to the firmware here. Here are a few photos of it next to the original board (thinner and flimsier).
I also decided to remove the top plastic cover on my keyboard to give it a more naked look and taped up the controller to avoid shorting it. I plan to make a transparent acrylic laser cut cover for the Frosty Flake.