I'd stick with rim brakes or discs...carrying parts and dealing with 2 different brake systems on a touring bike doesn't make a lot of sense.
Aren`t the cables and levers the same for mech discs as for Vs? If so, that only leaves one more set of pads to carry. And that`s only if you want to. As for me, I`m sticking with V brakes or side pulls on all my bikes just `cause that`s what I already know.