105 is nice stuff, even the 9-speed versions, and there is a used parts market for them. Your most valuable components should be the wheels, but there is a robust market for 9-speed shifters if they are in good shape, and because 10-speed has replaced them, there is a good second hand market for older shifters that can be used on 9-speed tourers and cross bikes.
Why not just buy a nice steel frame from Soma or Salsa and make a new bike for yourself?