Looking great , but one thing...
You have used the one of the canbus pins hc2?
Either leave them clear to the expansion or ideally make provisions for the can transciever ( a very small circuit I'm sure you could squeeze in) . More people are asking about can now and the teensy has a lot of canbus support already in the current firmware
Quantum Coupe with V04 on Ford 1.4CVH,Quantum 2+2 with Custom V04 on Jaguar 3.0l AJ30 V6
mini GPIO :done More soon
CANbus broadcast interface: done
Simple sd logger :done
External CAN io: Inputs :done
Gearbox controller: working