You need a fan that has duct connections on both the input and the output, allowing it to be placed absolutely anywhere along the duct run. These are called in-line fans. You install a round grill on the ceiling of the bathroom, connect the ducting to that, run the ducting around your attic renovation, connecting to the motor in the small roof section above the new attic, and then out. My preference is to avoid all that cold attic area and put the exhaust grill on an inside wall of the bathroom, run the duct into the basement, install the motor someplace convenient in the basement and run the exhaust out the bottom of the house. Not only will these in-line fans go anywhere, but they are powerful enough for long runs and you can put multiple outlets on the same run, such as venting the basement bathroom at the same time. Some models have an ingenious backward inclined airfoil blade that makes them whisper quiet and dust-free.