I was going to build a hinged false seat bottom out of plywood to use as a storage area for tools and stuff, and just cover it with some padding or just carpet pyle material, then do the same with the seat back area with just thin plywood and carpet pyle.
I decided to put my factory seats in there but would rather have the stowe area since nobody can use the rear seats unless they are contortionists and like crawling through roll cages and don't mind a cross bar in the face in the event of an accident. LOL.