[KenWittlief]

I dont know if I would call this 'completely redo'ing' the robot.

The sprocket change sounds reasonable, but keep in mind by making it faster you will lose torque and ramp climbing / pushing power. You might get it all changed over and discover your robot has trouble moving from a dead stop, can no longer turn without playing morse code on the breakers... You will have very little test and debug time, and you may end up putting it back the way it was to begin with.

As for the shooter, you have a rules issue. If you did not ship the shooter with the robot, and it has not stayed with the robot from regional to regional then I dont think you can show up at the championship with the whole subassembly. The rules clearly state that you must ship the entire robot by the ship date. Any thing you add after that must be fabricated during the fix-it windows, and assembled at the event itself.

So even if you did build the shooter before ship date, and removed it before it was shipped, I dont think you can now legally bring it to any event.

you could bring the raw materials and fabricate another one just like it at the championship. That will be legal, and much more difficult to accomplish.