Looks good. Nice detail on the CAD. At first I thought it was too bulky, and then I realized I've been looking at asid61's swerves for too long and that this is fine.
A lot of the bulkiness comes from the shifter. I'm not sure about shifting speeds by crashing spinning gears into each other. I vaguely remember someone prototyping that awhile back. Did it go well?
The chain run from the shifter to the swerve module goes on shafts from 2 separate parts. Do you have the manufacturing tolerances to make sure that these 2 parts line up? If not, might as well add a tensioner.
On the swerve module, it looks like you're doing a lot screwing into the side of .25" sheet aluminum. You can make the bolt bigger and your life easier by cutting a cross into the side of things and slipping a regular nut in there (no tapping!) like this:
http://www.instructables.com/id/How-...tted-Insert-N/
That link is good for other stuff too.
Do you plan on actually making this, or is it a practice thing?