I don't know. The wood strips may be just as heavy as plywood. Do you mean a continuous covering of wood strips, or space apart?
If the structure was designed correctly to be flat wrapped, then it would be a lot easier to use plywood panels. Your idea may be too heavy for an ultralight (USA part 103).
What I have been thinking of is several plywood bulkheads to form the basic shape of the center section, with some stringers to tie them together. Then cover with thin plywood. This would be 6 or 8 feet wide, out to the wing stubs. Then the outer wings would be conventional ribs and spars, covered with the same ply.
i don't know when or if I will ever build a flying wing. I need to finish my current build, which is going slow at this time.
Jim