After the recent setbacks with stepper motors, I decided to focus on optimizing the two simplest forces at play: friction and torque.
The amount of friction increases when weight is added. After adding a few pounds of weights to my vector bot, the added friction on my axels was too much for my motor torque to overcome. The best way to reduce friction in my case was to add bearings.
After purchasing new motors and motor controls, I set about designing and 3D printing the new robot frame.
Vector bot in the sphere: