Yeah, this made me wonder, in lieu of a lung transplant, what if they just took out a smoker's lung and gave it a good wash and then stuck it back in again? It sounds like you are saying that alot of other things go wrong with such a lung, not just a buildup of tar.
Or leave it in and use a splash of perfluorocarbon to prophylactically rinse it out a bit, once every couple of years or so.
Even if the breathing liquid does not dissolve all the lung crud directly, the mechanical action of filling and draining the alveoli might clear some of it out or thin it enough for the cilia to move it.
At the very least, once the carcinogens have done their job and induced a cancer washing them out would be a bit of "shutting the barn door after the cows have run away".
