From experience (most of my bikes are kinda like this):
#1. Bar-end shifters for the drops? You can run (most of) them in friction mode (if you want / need to, and they really will shift pretty much anything like that). They aren’t especially attractive set-up on bar-cons, but you could do that too on your flat-bar set-up which might (!) save you having to fanny about with swapping gear cables at all when you switch bars. My choice is the Dura-Ace 9sp SL7700’s (on friction).
#2. Maybe … install cable-operated calipers anyway, they’d work fine (with the right levers) on flat or drop bars. BB7MTN need V-brake levers, the BB7Road will operate off normal road levers. I dunno the Tekro versions, but the Cane Creek Drop V levers are a nice match for BB7MTN.
#3 Moustache bars might be a decent half-way – I’ve recently stuck a set of Mungo’s on my Peregrine and it feels great (so much so, I’ve done the same thing to/with my Fratello).
#4. Bontrager do a 17° stem in a range of lengths, you might find you’ll need a bit more rise than you’d think to get comfortable.
#5. Salsa’s new Cow-chipper ‘bar looks like an interesting ‘bar – Midge’s are always a solid choice for this kinda thing.