Can you paddlock or bolt the frame and joints together? I have no idea if that will work. I have never put one together.
If you keep the frame tight and bolted together, can the canvas come off?
I thought about this idea as well, I think that it could work, because all you would really need to do is make the modification visable enough to make the theif realize that its gonna take some serious work to get the frame apart. If you could weld some eye bolts to some of the major joints and run a bright orange painted cable through several of the vertical and horizontal runs. It could be as light as a Stainless Steel braided 1/4" cable, and I've even talked to a canvas seamstress about sewing a 1/8" SS cable down the ridge of the tent, then leaving a loop or another eyebolt to put a padlock from the frame cable on either end of the tent.
Or maybe once the tent is set up run a heavy bicycle cable from the sewn in cable to the closest tree of decent size.