I had an old road bike frame with the shifters mounted on the down tube. I like the frame because it was quite light for an aluminium frame, only about 1.7+ kg and the aero design. Since I prefer disc brake rather than calipers brake, I decided to rework the frame so that I can use disc brake plus some changes to the cables routing and an additional water bottle on the seat tube. Here are the brief details of the work done;
Brake cable runs through inside the top tube, cable holder welded on the seat stay, mount for disc brake welded and extra water bottle cage mounting on the seat tube created. A slice of 8 mm aluminium tube welded on the seat tube, to make it thicker, before holes were drilled and tapped. Also mounting for the side stand on the chain stay removed
Old brake cable holders on top tube removed as also the mounting for shifters on the down tube. Stoppers for shifter cable housing were then welded underneath. The carbon fork bought from Ebay and cable holder fashioned from aluminium tube glued to it with resin
Here is the finished bicycle, a Gravel Bike running 700x32C tyres.