I think this is why in Japan, you shower before getting into the bathtub... my host family basically had a bathtub that was always full and circulating water and always heated, and you could hop in any time. (Obviously this is not a good or workable solution for you necessarily! Esp. since Japanese bathrooms are designed to have the shower separate from the bathtub.)

I really do love soaking and find it really relaxing, but due to all the reasons you list above, I usually go to Asian-style bathhouses and dunk myself in various tubs and hop in the sauna every so often. (There's one in SF if you are inclined to just try soaking without thinking about cleaning the tub, but I am guessing that is not what you were asking for?) /is unhelpful