Ok, here is the basic layout. The light grey areas. Imagine those as a bit of a shadow if the light was coming directly from the top of that view. The idea is to bend the bumper like the ARB does. Not perfect I know, but maybe gets ideas going on the final design. This was done up in about 5 minutes, just to get my idea out. Hard to show the corners without going 3D. As you can see from the back view, the design allows for a bit of a step on the side as well, since it is wider than the bottom of the bumper. The area in the back also shows where the light mounts should be. I see the light mount having a tab at the bottom inside the bumper. Instead of just one hole, there would be a tab with the hole being an oval going back into the bumper to allow for an adjusted depth of mount. The side view shows a bit of how I see the angles, again trying to match to the ARB style. The top view is really hard to show here. I basically shows that the bumper should go back more in the middle. Bends in the back along the bottom edge, where they go up, and where from the top view they go in back towards the corners match up.
Because of the additional space in the back area, large tubing could be used. I would expect the middle section to be about 6-8 inches high, and then angle back under the rear at an angle that would meet up to be in line with a gas tank skid plate. Because of this large area, it would be closed tubing, to allow for air storage. There are a number of possible areas in the corners that would allow for a tap into that area for an air connection.
Any questions or comments, please feel free to contact me at firstname.lastname@example.org follow a thread on this design in the jeepsunlimited.com forum