[Deke]

I think you have gotten some good feedback, just a few more comments for you.

You can use flat head bolts and countersink the outside of your plates to clean up the surface, that should help when you actuate the module up and down so nothing catches. Also, the inside can be counterbored slightly to keep the standoffs from sliding around. Then the standoffs can be tapped on either end and you can save money and weight on shorter bolts by not running them all the way through. The piston can also be attached to one of the standoffs, so the big shoulder bolt doesn't have to be used to save weight.

How are the axles retained? You may need a bit more space added for a retention method. One option is a retaining clip between the pulley and wheel, that will keep the axle from moving either way. The down side is that creates a stress riser in the middle of your axle, but it should be okay since it's not cantilevered. Or you could get rid of the live axle on the traction wheels and go with a dead axle setup, that would solve the retention method and get rid of the hex bearings.

There was one module I saw before, I don't remember which team it was from, but it was packaged nicely. They had a CIM driving a gear on the mecanum wheel and the opposite side ran a belt to the traction wheel. Then the gearbox was packaged right into the module, it eliminates the complexity of a separate gearbox and hex shafts/bearings with dead axles. It just depends on what you want to do with the module.

There are a lot of design decisions to be made. Have fun with it!