Remove the meter. Why not just skip metering all together.
So some 'black' any target IS zone one. Is that your intended
meaning? A black worth it's salt should not even register on
many meters.
A second point: Generally non-linearity is a characteristic
of electronic instruments at the extremes of their
measurement capabilities.
Then there are matters concerning real world in the field
metering which do not mesh with film speed determinations
based upon the metering of some who knows how black
black target. Dan