I think the yellow is going to move the sky down half or one Zone, the ND grad, if judiciously applied, can bring you down another Zone. But the ND itself won't reduce the contrast between different subjects within the same band of density, it will reduce the contrast between anything in the clear contrasted to anything in the gray. But you will see that.
You can count Zones just like that.
If you don't like graduated Neutral Density filters, then don't use it. You can always burn the print.
I usually disregard the high readings of sky when considering N+ and N- development, I count what's important and allow those spectral highlights to fall where they may.