Would tiling a basement floor provide any effective moisture barrier?
Depending on your location, basements will emit moisture in some degree or another. The concrete floor may appear dry, but moisture does pass through it and into the room. A tile floor probably wouldn't prevent moisture from reaching the room due to the grout joints. I've heard about heavy duty concrete sealers, but that would prevent bonding of the thinset when its time to tile. I've had very good success installing treated sleepers on top of plastic covered by plywood.