Looking at the pictures you have direct drive and massive pinion size. This will cause you troubles. First the large pinion will give huge pitch size so resolution will be very low.
Worse is the affect of the direct drive with no reduction. You'll struggle with torque and Resonance will be high which could affect motors. The digital drives will help but still your upping there work load which isn't good.

My suggestion is to put minimum 3:1 Reduction using Timing belts/pulleys. This will give more torque better resolution and lower resonance. If not your going to struggle with all those things.!