Where does the sewer come into the house under the basement floor ,middle of the wall ,or at grade? If there would be enough space to run the pipe at 1/8 inch pitch for 50 feet or 6 1/4 inches(min. pitch for 3 or 4" pipe). If you have the room then you will have to run vents up for the new bath. Most homeowners want the unsightly roof vents on the backside of the house (attic work)
. Moving a bath in any home is very pricey.