I would be concerned about bacterial growth in the R/O unit and on the R/O membrane if it has been sitting in stagnant water for a year. If it is dried up, you'll need to replace the membrane as Dan said.
As per lining your stand with foam insulation, the only big concern is heat, but if you have good ventillation, it should work for you.
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32"x32"x20" Cube-ish tank
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