I like what you did with the under apron pocket. I do a patch pocket roughly in the middle of the under apron but your design is cooler.

You might consider sewing closer to the edges of the pleats. IMO it looks a little neater, and along the fell you won't have those flappy edges where the pleats are sewn down. I use a 1/16" compensating foot, which is just a guide to make sure my stitching is straight and an even 1/16" from the edge. When I still sewed with domestic machines I used a blind hem foot, which worked great.

If you've got more kilts in the pipeline you might pick up a bias tape maker for your belt loops. It's a huge time saver, dead simple to use, and will let you ditch the zig zag down the center. I have a 1" and 2", which gives me .5" and 1" belt loops. I think they were maybe 4 bucks each.