You used to be able to get either derailleurs or a little widget designed to anchor the end of the cable housing on to the cable clamp on the FD, and the cable would run down and get fastened tot he bottom brakcet... this allowed bottom-pull derailleurs to be used with top-tube cable routing. This was common on Treks from the early-90s, not sure about other brands, or availability of the part or FDs aftermarket.