I like my antique 20-35,, so compact and built like a tank. or in my side pocket, I'll throw a 20mm fprime afs or a 28. The D800 is already fairly heavy, so I like lightening the package with primes.
My favorite is a small belt lens pouch just big enough to carry the 20-35 2.8 or 35-70 2.8 which are both light lens and with that combo, have a nice carry around package.
for wide angle consider a 15mm prime, or 16 mm prime, still way lighter then these big wide angle zooms.
if weight is no issue, then the 16-35 does sounds like an interesting lens but I have heard mixed reviews once it is open beyound 20mm, which seems like the whole point of dealing with a heavy lens. I am interested in this lens, but a bit worried about its performance wide open before investing serious money.