i like the thought.. but i dont think you will be happy with the amount of room back there once its all said and done, i know id also have to find something to do with the panels in there, that unfinished look back there would drive me crazy, maybe tidy up the wires and rhino line it?
if it was me and i knew id never use the back seat again, i would build a mount to hold the spare tire upright behind the front seats and make a very thin false floor across the back of the whole cargo area so i could lay tools, rags, fluids flat underneath it and still have a flat cargo area