Have you considered just going with a mechanical? BB7 road?

It will still give easier brake pull, and will let you use standard drop levers, allowing you to have your hands in a stable location, what you want for downhill anyway. Normal mountain levers are large enough I can't imagine it working very well on the flats of a drop bar.

I've run a front BB7 on a fixed and geared road bike with good results. I have not used hydraulic brakes.

Get paragon sliding drop outs for the rear! So you can simply swap out the sliding plate for a disk compatible version in the future if you like.