I'm not sure aluminum would be my first choice for a tire carrier or anything not 100% solidly fixed. Aluminum is not as fatigue failure proof as carbon steel is, so any deflection in an aluminum piece is a cumulative stress that adds to its eventual failure (cracks).
Very good point. I've wondered about that...in my perfect world, I'd love to have a custom aluminum bumper fabbed up with 80% of the bumper being aluminum, mostly the plate surfaces that would wrap around the rear fender. The framework bearing the weight of the tire carrier would be made of steel. Instead of one long swingout, I'd have 2 swingouts, one on each side to distribute the weight. One swingout to carry the tire, the other swingout would have a gear rack for fuel cans or whatever. Each swingout would have a fold down table on the inner side, like the bumper BLKNBLU showed. THis would give me three work/cooking surfaces with the rear tailgate down, and I wouldn't need a whole parking space reserved behind the truck to enjoy it. The only problem is finding a fab-guy who's up to the challenge...and $$$ of course. I'd imagine the aluminum parts would have to bolt to the steel so it'd be a slightly ugly franken-bumper, but oh well.
Points to ponder:
Another possible solution is the ZUK Mod. Search it on Yotatech and you will find several threads about it.
http://gearinstalls.com/dc.htm
Some folks consider this totally hillbillie but most that have actually done it seem very happy with the results. To me an advantage is that you can get coils at different spring rates for different needs. Going to Argentina with a ton of gear? Put in heavies. Driving around the Rockies for backpacking trips with minimal gear? Put in something lighter.
I did the weldless Zuk mod, with front coils from a '97 TJ...The total lift was about 2-2.5 inches in the rear, which was sagging that much to begin with so I'd look at it as more of a cheap leveling kit, than a lift. If I didn't cut the coils down to 14", it'd be much higher. With 235/75R15 tires on stock wheels, I have about an inch of clearance between the coil springs and the tire sidewall.
I couldn't afford an aftermarket lift and I couldn't stand the saggy rear. I like the fact it is completely removable with no welding or drilling. It may be "hillbilly" but it seems to be the best bang for your buck. $20 bucks and super simple. I've noticed the ride quality has improved a little, especially when I've got about 300 extra pounds of gear in the back. I will admit that I was pretty freaked out trying to pack those springs in between the leaf packs...those spring compressors are sketchy at best. I've loaded tons of gear back there and it doesn't appear to sag.