You should appreciate that light rays at an angle of more than 56 degrees are not going to be affected by the polarizing filter and so you will have images with the center showing the effect of the filter but not the edges. When you consider this limitation and the need to shoot at about a 90 degree angle to the sun and the use of such a filter on the 14-24mm lens is extremely limited. I can see some value for a graduated ND filter if one is available that is large enough to work but even then there are alternatives that work better in the field.
Why do you assume I would be using a polarizer to darken the sky? I would be using the polarizer to cut reflections off of water and vegetation.
Anyway, you are not answering my question, just questioning the validity of the question, which is not helping.
I have often wished I could have a circular polarizer on my 14-24, so my applications are wider than "extremely limited."
I have used polarizers on lenses up to 17mm wide (35mm equivalent) and I have been happy with the results.
I am not aware of the 56 degree limitation. Would that affect reflections off of green vegetation in a rainforest?
Finally, I can use bracketing and post-processing to achieve the same result as a graduated ND filter. I cannot replicate the effects of a polarizer in post-processing.