AEV makes a rear bumper that can store liquid. I wouldn't use it for gasoline or drinking water, but hand rinsing water can sure be handy on the trail. They also have a setup for 2-5 gallon plastic rounded containers that fit unnoticed behind the spare.
I've also seen setups for dual spares, and gas cans that tandem out the back of the spare from recessed in the wheel. All that and a couple of jerry cans beside the spare(s), a high cooler rack, and somewhere to stow a high lift and I'd be set, but I can't seem to find it all in one package, especially through someone that will install it all.