Finally a robot that even i will be able to CAD properly 
We have powerful electromagnets to pull the metal towards the center of the robot. Next we put in a super-cooling device, usually about 9mK (9 miliKelvin). This gets the metal to contract down into the size limit.
But during inspection, just to be sure it is in the limit, we greatly decrease the air pressure at the venue. This causes the metal to contract even further leaving us with a few micrometers to spare.
Don’t screw around. You screw around too much!
Dear Vex Vortex,
Your drive for perfection and ingenuity is truly remarkable!
However, there is certainly room for improvement:
First thing that caught my eye is motor controller - it is totally redundant as Cortex provides two motor ports with builtin H-Bridges. Please, remove it as it hurts my engineering ability to absorb the beauty of your design.
Another consideration would be safety. As cool as the concept of tether-bot goes (i.e. this years’ VEXU SYNC bot) you may cause permanent damage to your robot if an autonomous program goes wild.
Also, some judges may not appreciate falling signs as it could pose field safety concerns. If you will absolutely insist on not adding an extra screw, zip-tie, or a rubber band to the design - may I suggest to use the motor wire to tie motor, battery and signs to the cortex so that everything stays together.
Finally, pedantically speaking, the base subsystem may consist of a single zip-tie or a rubber band holding together cortex, battery, and signs (since signs could not play functional role themselves). But if you think that static base is too boring for your target audience and some action worth doubling number of the parts in your robot… Then, at least, consider replacing wheel assembly with a single axle twisted as a screw.
Then, not only you could reduce the number of parts in the subsystem, but add some forward motion. This will make your robot much more interesting to watch and, with a clever shape design, you may actually be able to push an extra cube into the neighboring base tile.
Truly yours,
Technik