A Home Depot customer asked how to put an old cast iron bathtub over a terracotta tile floor, without cracking the tiles.
My suggestion was to carefully plan the position of the tub so that she could put wooden tiles in the place of the four tiles where the feet land. The wood may dent with the weight, but will not crack, and since a tub is generally a permanent installation, the damage to the wooden tiles will never show. I used prefinished engineered flooring that was thinner than the tiles, so if you use these, you may want to shim up the wooden tiles. If you use regular wood, you will probably have to plane it down to the right thickness. Choose the colour of the wooden tiles to fit with the d?cor, and even if they are pre-finished, finish them with several coats of polyurethane to stand up to the moisture, especially around the edges.