A few things to think about, I posted some stuff like this on Chris's thread too. I've had my bike mounted to the rear tire mount for more than a year now, so have some experience with this. With 2 bikes and the 33" spare the rear gate will flex slightly at the mounting points even though they are re-inforced. A 58 qt cooler (75 cans) and 2 5 gal jerry cans is about 140# of static weight resting on the mounts. If you do nothing but drive on flat ground I have no doubt this won't be an issue, but I do believe that it will be an issue when off road, hitting bumps, etc.
I'm not trying to rain on anyone's parade here, but I actually took off the bike rack mount because of my concern over the flexing of the rear door. Your design looks real solid, and if I can see in the pics, you might even have two side braces that press up against the door? that would help take some of the load off the mounting bolts, but I still think a rear rack w/spare tire will cause problems when going off road.
If you can make the rear rack, why not make up a roof rack and put the spare up there? I did that, and it eliminates a ton of extra weight on the rear door and I'm sure you could load up that rack with all kinds of cool stuff and still have piece of mind!
my 2 cents...
