Our sanctuary crew or rescues have folded soft cotton sheets, towels, or low-weave carpet pads w/a layer of cotton sheets in their xpens or housing quads.
Every family member will enjoy the soft matting, rugs, etc. as long as you don't have a chewer of indigestible material. We learned the hard way when a n/male tackled a low-weave mat and got a severe GI obstruction. Personally, I won't lay on a rug-less floor anymore. I like comfort.
One rex gal we had, who at one time needed to lose weight, would get sore hocks on the bottom of her heel. The condition never escalated to the sore hock pictures in the link above.
Silva sulfadiazine cream was suggested to help remedy the pink, hairless area.
Good to know you are concerned about your bun!