First of all, I'm green with envy that your dh will be able to build you this wonderful sewing unit! How lucky are you? :D I think the ideas you've shared sound fabulous so far!! I especially like the light box/cutting area and the cabinets with the narrow areas for mats, etc. I have two baker's racks in my room that have wine racks and I put all my stablizers, freezer paper, rolled up paper templates, etc in there and they fit so nice. :)
IF my dh could (would?) build me a sewing unit, I'd be sure to have him add an area to my left to hold the bulk of my quilts as I'm machine quilting them. Right now, I just stick two sturdy tv trays next to me. That works ok for holding the weight of the quilt, but they tend to shift a little more than I like and I have to keep adjusting them.
Someday.....:D