I'm not suggesting that you can't use K2... Just that the filter factor might be surprising.
An idea that may work for you... Look up "Hutching Filter Factors" for a technique (not specific factors in your case) of light reading shadows through the filter, placing on shadow Zones, then applying a filter factor.
So work out the factors needed to get shadow detail. That's where you usually lose out (for instance with a red filter and normal pan film, blue shadows and red filter often combine to lead to unprintable negatives because of the double-whammy).
You say you'd refuse to have blank skies, but I allow for exceptions because there are plenty of landscape compositions that work fine without clouds.