So you have a strip that is maybe 8 yards long, by perhaps 8 inches wide? You also have a strip that is the full 28 inches or so wide and a few yards long?

Is that right?

And if I understand correctly, your plan is to use the full width piece to make the apron and under apron, attach to that some light weight material to complete the 'body' of the kilt with pleats, then cut the narrow strip into strips as long as the kilt and as wide as a single pleat right?
Then sew those strips onto the lighter material to give the appearance of uniformity?

If I understand correctly, its not too far off from how a Utilikilt is made, or one of Jeff's two toned Pittsburgh Kilts. Skip the backing material and sew the strips together directly, and you pretty much have it.

Uk's are made with each pleat being one piece of material as wide as the inner and outer pleat, sewn to the next pleat on the two inner edges, and then having the pleats outer edge sewn into the folded material.

It could work, but by flipping the thing strips vertically you are going to have cross patterns in the weave of the material, regardless of pattern or color. It would be better if the material was all the same grain in orientation, but it sounds like it could work.