Looks good to me. The only critiques I could make would be:
1) Have the skid plate go ahead and cover the torsion bars-it wouldn't add a ton of weight, would give you a better attachment area to the frame, and would also stengthen the skid plate itself. It also wouldn't really interfere with anything to any great extent as far as I can tell.
2) When you do the transitioning points(like wherever it makes a 90 degree turn in your drawing) I would try and do either a 45 degree or better yet an arc. This decreases stess points in the design. Just on the inside bends, not the outer corners of course.
3) I'm not sure what you are thinking of using for the build material, but if you go multi metal, you could use a ridged piece of thin steel to support a flat bottom of either aluminum or nylatron. This would make the skid plate assembly lighter overall, and enable you to remove and replace the aluminum or nylatron bottom whenever you got a deep gouge or crack. It's a little more complicated, but would be better in the long run I think. You could also cut all your access holes in the ridged steel and cover it up with the flat bottom piece so you don't end up having to drop the entire skid plate assembly when you need to get in there and look at stuff(i.e. oil, xmsn, xfer case, catalytics, O2 sensors, etc).
4) If you are having it fabbed up, then make sure they get it exactly the way you want it. Be there when they are doing it, so if they have any clarification questions, they don't have to guess because you aren't around to ask. I've seen a lot of botched installs due to "interpretation".