As most people in the high end today tend to build separate shower enclosures, next they should really consider installing the soaking tub in the bedroom, freeing space in the bathroom, maybe for a double vanity and a large shower with two heads, going back to an 18th century old tradition of installing copper tubs in the bedroom (no running water at the time), sometimes next to the fireplace. Copper tubs can hold two people. Tin lining inside a copper tub is a must to protect the skin. In the old days they used bath sheets to protect themselves. A good copper tubs has to be 14 gage to stand up well and last. Thin and cheap copper tubs wont come with a tin lining. Sometimes they are nickel finished inside for cosmetic reasons, trying to imitate tin which wont help with the skin. Fairly lightweight, copper tubs are easy to haul to the upper floors of a house. Tin lining the outside of a copper tub is available if you like the more ancient tin look compared to stainless steel. If your house can support the weight of a cast iron tub so be it. A cast iron tub can be painted in any colors to match your decoration. Stainless steel and copper skirted cast iron tubs look great in the bedroom. Honestly I think that the ultimate luxury is to have a large soaking tub in the bedroom where you can eat, drink, smoke, watch TV, breathe and more while taking a bath and entertain your guests like in ancient Roma!