The pull down Spare tire carrier is possible. I had done it with a CBI Off road tire carrier. The carrier cost about $250 here is the link
http://www.cbioffroadfab.com/index.php Go to images, then armor then Tire carrier. It does mount to your Hitch.
Then I modified it by welding it on top of my hitch, so I can still use the Hitch:
Here are more pics of the Tire Carrier and my buddy welding it for me.
I have taken this set up through many trail rides and had no issues with it.