Draining all the lines every time you use the water would not be practical or easy. How cold will your trip be? Most newer RVs have at least some type of passive air flow from the furnace to keep the pipes from freezing if it' not too far below 32F, and you can use a light bulb in the wet bay to keep the pump from freezing. A lot of it really depends on your particular RV. Most TT's are 2 season, maybe 3. Very few are truly 4 season. Without some serious modification and a LOT of propane, you might not have a lot of luck.
Also, your post might get more attention in the travel trailer forum instead of Class A.