sounds like a neat project to put together. Yes of course I recall your DC and all the various ratio graphs (gearing nerds of the world, rejoice-yes I am one)
a good find, I imagine you could sell the brifters and such to fund some of the stuff for this build.

all the best with first coming up with what systems to use for shifting, and then experimenting with positioning. I havent used trekking bars, so really only imagined them with the shifters and brakes set up like on a mtn bike, on the straight part of the bars, with the rest of the bar going forwards for diff hand positions--so again, have fun experimenting and visualizing diff setups.

cheers