If it is to be outside, you should consider some type of cover/roofing. Not only for sun protection but hawks or other raptors. I was planning on getting the coroplast for my indoor setup but due to various circumstances have yet to check into it myself. Well, that my newbie bunny mom's two cents, hope it helps.
Slippery surfaces for a young rabbit can affect their leg development and cause them to be cow hocked or splay legged. Horse stall mats are very durable and have a good surface but typically weigh 100 lbs. Have you looked at shop floor mats? They would also be made of rubber but are lighter in weight, easier to cut and may possibly come in something other than black...just a thought.