An X5 built for Dakar has no more in common with a street X5 than a M3 has in common with a M3 GTR.

The X5 (and the Cayanne) was never designed for off roading, and no matter what you do will not ever be a good vehicle of offroading. The problems start with the unibody construction. You cannot put sliders or skidplates on a Unibody if it wasn't designed for them to begin with. There is no strong place to attach them. Continuing on, there are not skid plates. The X5's suspension is also to delicate, the aluminium components would be torn up in no time in any serious off roading. Finally, the 4 wheel IRS as set up on the X5 is way to stiff and lacks enough flex to do any serious off roading.

There is far more to a vehicle that is designed for off roading than just lifting it. Take a look under a landcruiser at the size of the axles, how the vital components are tucked up out of the way, and the overall contruction and you will see there is no comparison.

There is a reason that Landcruisers are used around the world. They are overbuilt and exteremely reliable. There are many items that are specifically designed with that type of use. To give you a few idea, my 80 series has two fan belts to allow the water pump and fan to continue operating if one breaks. Many 80's also came with electric lockers front and rear. They are built with Birfield axles which are extremely strong and can be abused beyond belief before they break.

Every vehicle has its compromises. The X5 is designed as a vehicle that handles well on the highway and can be taken in the snow and on dirt roads. Landcruisers and Parado's are designed to be used an abused. No matter what you do, an X5 will always run circles around the Landcruiser on the road, and conversely, the Landcruiser will always be a superior off road vehicle.