Kaffenback smallest is still too big .. anything else? Disc is ideal for wheel size freedom.
Spyres are about £100 for a pair + 5800 shifters which are £115 .. plus cables; thats just £70 less than R685.
You sure? it got a very slack seat tube on the smallest model, so reach is similar to the drawing, smaller than the smallest Straggler (R: 377mm S: 534mm)
Planet X is cheaper tho.
BB7 road or TRP Spyres.