As you say screwcutting takes care but it is possible.
The voltage regulator you show will not work with an induction motor as fitted to the MD65.
The slow speed system helps but is not the complete answer. The problem is the stopping time, the standard motor has quite high inertia and takes a while to run down when just taking a light cut.
Two possible solutions:
1) Make a handle to fit in the back of the spindle and turn by hand for screwcutting.
2) Change the drive to a 3 phase motor and inverter as described here:
**LINK**