I'm using hydraulic brakes on Trekking bars . Believe me It is not difficult at all to move your hands

back to where the levers are , quite quickly ..

you cannot daisy chain hydro disc brakes .. but you can do a primary and interruptor lever on the same cable.

I just question, other than on drop bars, Why? .. going to use the rim for parking brakes?

(would be better than gripping a Hot Disc, and holding it on.)