Here's another thought, and seriously, it's an interesting one:
The D5500 is Nikon's hidden gem. It has a great 24 MP sensor, features a "flat" colour profile for video as well as stills, a fold-out touch screen, HDMI video output (8 bit 4-2-2), 1080 60p, a decent grip, shoots 5 fps (only 6 RAW frames though) and weighs around half of what the D500 weighs, at 420 grams including battery. Max shutter speed is only 1/4,000s and the viewfinder is tiny, so one is basically limited to AF, but I've looked at a couple of RAW files and they are surprisingly close to those of the D810 in quality and flexibility.
Reviews are here:
http://www.dpreview.com/reviews/nikon-d5500
and more importantly here:
http://blog.mingthein.com/2015/12/21/review-the-nikon-d5500/
I played a bit with numbers to see what a complete D5500 set with 2 bodies and all lenses I would need for my "normal" travel photography would cost, and came up with a total of $4,700. That might sound like a lot for a plastic amateur camera, but look at the list:
Nikon D5500 x 2
Sigma 8-16mm f/4.5-5.6 (12-24mm eqv.)
Sigma 18-35mm f/1.8 (27-53mm eqv.)
Sigma 50-100mm f/1.8 (75-150mm eqv.)
Tamron 45mm f/1.8 VC (68mm eqv.)
All these lenses are of extremely high quality, and totally sharp from wide open (the 50-100mm hasn't been reviewed yet though). When I look at what I would need to pay to get similar image quality from an FX format camera, this is certainly food for thought. Obviously, one or both of the bodies can be upgraded to D7200 or D500 with increased functionality, no reduction in image quality but increased weight, size and price.
The package with 2 bodies weighs in at around 4.7 kilograms. It's impossible to find an identical package for FX, since none of the zooms have equivalents for the larger format, but it's an interesting setup all the same. A D810 with a 70-200mm f/2.8 costs $4,900. Add a second body and three more lenses and then... would anybody see a difference in image quality? Functionality yes, but image quality would be a hard nut to crack.
Just wasting some time in the morning