Mount Whitney is a great hike. I did it a few years ago. My wife and I will be celebrating our 25th anniversary in Evolution Valley, just over the ridge from Whitney in a couple of weeks.

Now, regarding a lightweight kilt for backpacking, specifically, I'm not sure there IS one, yet. However, if I were to make one I know some things about how I'd go about it.

NO SEAMS over the hips!! There's nothing like a bulky seam under a hip belt with 50 pounds riding on it to give you abused skin in no time. So any pleats would end at a pleat-less, 3-4 inch wide waistband.

A narrow apron. Say, perhaps about like a Freedom Kilts apron.

Built like a tank, but the material has to be lightweight. A solid sotton/poly twill would work. Stitch that baby down good. Build it out of material that doesn't show the dirt too easily. Medium-dark gray works well.

A "sporran" that can hang below the packs hip belt in front, but doesn't have to wrap around like a regular sporran, or a fanny-pack worn backwards would be great. I'm not sure how to carry that off, though.

Side slash pockets like pants pockets, great. Big mondo pockets on the outsides of the legs, banging around??? NOT. Butt pockets would be fine. Just keep them well below the level of that pack hip belt.

I could go on and on and on.