Very very cool. I'm enchanted! Do let us know how it turns out.

Here's the model railroader in me speaking: Turnbuckles were used in early truss bridges that used steel rods in tension, e.g., for what is called the "bottom chord." You (and the bridge-builder) have to make sure that the wires (and rods) are tight enough that they never slacken during the stress reversals that occur in use. If they go into compression they will fail. (When a heavy locomotive pulling a high-speed train comes onto a bridge, parts of the bottom chord that is normally in tension when the load is just sitting motionless on the bridge will experience compressive stress, sort of like the bottom spoke of a bicycle wheel does.)

Wire can be made to carry very high tension. The weak points I would think will be the attachments to the frame tubing which have to bear that high tension while exposed to the elements. (This was the problem with rod-truss bridges too, and they were too "bouncy" to bear the oscillating impacts of the really heavy steam locomotives that came along in the 1930s.)