Hi PanSat team!
Here are the schematics of the Qbcan board.
If you want to integrate more sensors you can do so by connecting them to the provided Arduino Pro Micro (using jumper wires or a female header for example). If you want to have a PCB integrated into Qbcan you could design it as a shield that is soldered on top of the Arduino (or uses female headers for a less permanent set-up)
Most of the Arduino pins have been left unconnected and thus are available for your use. It is then straightforward to integrate other sensors while maintaining the current Qbcan configuration. By keeping the Qbcan board as it is you can guarantee the basic functionality and we would be able to provide support in case you run into any problems.
If you still decide to modify the Qbcan board we would love to see your design!
Let us know if you have more questions!