The PCB that I designed and ordered from OSH Park arrived. The design is in the Github repository for the project. I have assembled it, applied a minor fix (forgot to route traces for the programming header), and tested it with some basic firmware.
The design uses an RN-42 for Bluetooth communications. It is what lets Keychange emulate a Bluetooth keyboard and mouse. On the other side of the board is an NRF24L01+ 2.4 GHz transceiver module. It will be used for communication between two Keychange devices so that one can be used per hand without wires connecting them. In the middle is the Atmega32 that runs the show. To the side are connections for the buttons (there are extra connections for prototyping), for the joystick, and for the battery module (a LiPower boost converter).