Back to the original question ...
looking at a spare parts catalogue for weather instruments
in the distance past, I recall seeing that they offered a rotor
with larger cups to boost low speed capability. This is obvious
when you think about it - bigger cup -> larger force -> more
torque -> better ability to overcome stiction.
If you move the cups closer to the axle, the faster the rotor
will rotate for a given wind speed. However, you then reduce the
torque. There would also be interference effects come into play, reducing
the performance.
Cup anemometers have problems in gusty weather where the rotor
inertia causes overspeed indications at times