Yes, that would be quite easy to draw up and mill, and one could easily adjust for differing widths of plywood — you’d just need an endmill smaller than the rabbet — also, unlike on a table saw, one could do a stopped rabbet pretty easily.
I’ll see what I can do to model those when I get a chance.
FWIW, I’ve done similar boxes in the past: https://forum.shapeoko.com/viewtopic.php?f=30&t=2796 (used to be project #1 on the old Shapeoko Projects site)
and c.f.,
https://wiki.shapeoko.com/index.php/Carbide_Create:_A_Simple_CNC_Box