Is it better to have a tool sit on a shelf and never be used because its not done?
I see your point, but a "CNC" that won't stay in the calibration (torque x inadequate support = tool drift) is worthless. At the very least, work will be substandard and materials wasted. Taken to the extreme, such a rig up might even be dangerous. Is a crappy tool better than no tool at all? (I know where I stand.)
The solution is to finish the tool properly or get rid of the pieces--despite their perceived "value". A case could also be made for "crating" the bits and storing them in the loft provided there is a firm commitment to complete the project within a reasonable time frame.