In my own designs, the spars (usually 1/4 square) serve to build a straight wing! Wing jig is steel rods, but the spars, once glued in, assist in holding everything steady while the sheeting, or T.E., cap strips, etc. are put on.
I can'r see any good reason to eliminate spars. If weight is a concern, realize that balsa spars are the least of your worries.
F.C.