Ive seen a few with rear door mounts and even bought one myself. But once i looked at how thin the rear door is, i decided against it.
Ive also seen receiver hitch tire mounts but then that might inhibit the door from opening fully.
There are a couple companies that make swing open bumper mounts; alluminess, weldtech...but they are expensive.
I have the Aluminess which was pretty much the only option when I was doing my build. It's ok. Pretty over priced for what it is but they're the only game in town. Mine was pretty poorly packaged and came with a few scratches. They also used the incorrect size lugs for a Chevy Express (Ford size maybe?) and the extra Gorilla lug nuts I had wouldn't fit. I really wanted to carry matching spares rather than two different patterns and after multiple phone calls they finally sent a new mounting plate with the correct size lugs. The carrier has been relatively trouble free once installed and is secure. Keep in mind it only allows the rear door to open halfway.
The factory location works pretty well, with some very slight modifications you can put almost a 35 inch tire under there. But then again the tire winch has its own set of troubles.
I have a storage box that I mounted to the rear door of mine, I copied Johnny5. The factory hinges on an Express door are really pretty beefy. I have had 30-40 pounds hanging off the back door for two years now. Even afree backing into a tree the hinges work just fine! I have no reservations hanging a spare off of the back door like Jonny5 did.