Nice work!
I have been thinking about something similar, for kitchen cabinet drawer bodies.
For this application, the drawer sides would be 3/4" solid wood, or plywood with edge banding on the top edge.
The bottom would be 1/4" or 3/8" plywood captured in a groove.
The box joints would be a "hidden box joint" so the joint is not visible from the sides, they would be covered by the drawer front.
This is accomplished by making a partial-depth cut on the side pieces, and a corresponding notch height on the front/back pieces.
Other useful features would be holes for the drawer pull, and notches in the back for blum bottom-mount drawer slides.
Any interest in adding this to the plugin? I can help out with the details.
Cheers - BillT