As far as departure angles, I would think that the tire will sit high enough that you would lose cladding first? I think the pics of Tom's may be deceiving do to the huge offset he has as well. That tire is wide!!!!! Plus, if you have a hitch back there, that takes all the hits anyway. I suppose my hitch is more of a rear skid plate than an actual hitch.
As far as legwork for the mount, I am gonna go to the junkyard this weekend if it ever stops raining and take a look at some rodeos and troopers, maybe some older Pathfinders or 4runners if the bolt pattern is right. I will let you guys know. The more I started thinking about the stress on the roof rack, the more worried I am getting. If that thing comes off while driving...it will kill someone. That does not sound like fun in my book.
As far as door deformation, I think a backing plate is very important to distribute the stress, and as Tom said, be careful when you open the door, and keep it lubricated. When was the last time you lubed YOUR rear end?