Just want to say, long time lurker here on the forums. I have decided to create a button box for simulation games, and wanted a good amount of buttons. I thought this may deserve it's own topic, as I am combining two Pro Micros in one board. I have reviewed the circuit, and it looks solid to me. I wanted to share, as well as get any advice before I order a few boards to test.
Any help is appreciated!
Edit: Added additional photos
The top traces are a bit narrow, bottom traces, we cannot see.
A copper pour on the component side is not necessary, doesn’t solve any problem.
There are Encoders that have push switches.
Power LEDs are nice to have.
Mounting Holes are nice.
1206 SMD diodes would have been good to use.
Where do the Micros get power ?
Using TX and RX might be a problem.
Really appreciate the quick constructive feedback!
Here is the top and bottom together with changes:
Why two Pro Micros? You can use port expanders and shift registers if you don't have enough GPIO pins.
On a 32U4 based board (like the Pro Micro), those pins are not used for usual communication with a PC; so I'm not sure where you see a problem 
32U4 based boards (and most newer Arduino boards) have USB hardware in the microcontroller and that is used for communication with the PC over USB. The Rx/Tx on those boards is connected to the UART and can be used for something else (similar to the additional UARTs in a Mega).
Each Joystick device needs to have 32 buttons or less. Otherwise I have to use vJoy and UCR configs. I would prefer not to do a bunch of software configuration to have these work with various games.
