I just had an idea for water storage, but not sure how practical it would be. Basically, find a tank roughly the same dimensions as the spare tire location and use the tire crank to hoist it in and out of place before/after trips. Maybe too great of a chance to break it while wheeling, but you can find some fairly thin marine tanks. I was looking at a 10gal, 32" x 19 1/2" x 4 3/4". That should tuck up there nicely. The other concern is that it'd get filthy with mud and grime. Might be good for emergency water at least...
Thoughts?