I think the problem right now is how to handle the left and right ends of the OEM bumper. The SW Xterra rear is just the center section, as the Xterra has a 2 piece OEM bumper. This being said, you would have to cut the center section off of the OEM Pathy bumper cover. Until I see it in person, I'm not convinced this could be done easily to be made to look good. The newer Pathys have a slightly different rear bumper cover that matches the 2 lower corners of the rear door. On mine these are curves, while the new Pathy's have straight angles. These would be a lot easier to "cap", or even cover up by attaching larger plates on the ends of the SW bumper.
I'd like to see a SW Pathy full rear bumper that includes the lower rear quarter panels. It'd be nice too, to see a step like the Xterra has incorporated into it. Full metal wrap-around design, multiple recover points, spare tire relocation, increased departure angle and a mounting base for additional add-ons and an integrated rear step. How nice the thought!