I see what you did with the low speed
On to the actual design. It looks like in this design you can actually get rid of the idlers and still have enough room. there seems to be ~1 inch of gap between you bigger dog gear and the body of the CIM. getting rid of that idler gear would be great.
Second, we use FESTO for pneumatics, as they generously give them to us free of charge. So see if you can use a festo piston instead of the one you are currently using.
Overall looks good though. the shifter sticks out of the frame, but it should be well protected by the CIMS around it.
Ill take a closer look at it in person later.