Now as far as the IRS unit. I will be honest. I have never seen the rear suspension system of the VX. I only know how hard the vehicle rides. Many many SUV owners never see a bush or mud unless they live near the Cali coast like Malibu. So why not try and find a way to give a sophisticated imaginative unique vehicle a sophisticated ride? No, Rock crawling would be out of the question, but isn't that what chopped up Jeeps are for?
With all this talk about reverse cut pinion gears meshing with ring gears etc it would be easier, less confusing and probably the same cost as dropping in one of those units in Kodiak's note above.