In a practical sense, I doubt that movement would be at all fluid in the system you propose. The pen would only move when the magnetic force on the second motor was high enough to overcome the friction losses. The result is non-fluid movement, or no movement at all if the input was subtle enough.
The second part of your comment doesn't make sense to me. Digitization artifacts are a function of the A/D conversion, not of the transport mechanism. Over a telephone, that is remedied by time.