What about a covered litterbox? Mimi shredding the wallpaper in a bathroom of a rental house once, due to scratching around, and I had to pay to rewallpaper the whole room!
She isn't as bad now as she hardly ever has to use the litter box. She is an indoor/outdoor kitty. But when it is cold and I have to leave her indoors, I make sure to pull that litterbox away from the walls. She scratches everything, but the litter! I was thinking one of those two piece boxes might work for you.

Good luck. Let us know what happens.