My old cube stand, I sealed and epoxy coated the inside. It'd hold about 20 gallons of water before anything hit the floor, and then I put a cheap battery powered water alarm in the bottom. When I sold that system, after 2 years or so, the carpet and sub-floor underneath it was in perfect condition.
My new system sits on a steel stand with a waterproof top. No equipment under the tank, the sump and all are in a closet behind the tank. Carpeted. I try and keep things off the floor, and I did toss my water alarm in there... thought about lining it with rubber sheet and putting in a drain line, but I didn't do it. More worried about humidity in the closet than I am about floors. I've got a portable dehumidifier in there... that works, as long as I keep the collector emptied.