if you have porters to lug your stuff, this is the perfect time to splurge on a 200-400 or a sigma 120-300 (if you're
watching your budget), right? alternately, you could just get a TC for the 80-200, which you may actually find not long
enough. you appear to have all the other focal lengths covered, except 55-80 or 70-80, depending on which zoom
you take.
if you were going ultra-light, an 18-70/70-300/50 set-up would be optimal, but since you have help and are insisting
on the 12-24, the strategy changes.
really, i think you could do the trek with a bare-bones 12-24/50/80-200 kit in the mountains; in the cities just add the
35/2. the 18-70 is nice and light, but slowish. again, you have porters, so conceivably you could take the 17-55. and
nice as the 85 is, that seems the most extraneous of all your lens choices.
a backup camera is also a good idea. if you take a film camera you might want to pop the 35/2 in the bag to pair with
the 50. unfortunately none of your DX lenses will work on film, so that's a major consideration.
along those same lines, if you go for a d700, all of a sudden you have nothing for the wide end, so that's not a super
great idea unless you want to pick up a 14-24 or 17-35 too, although i suppose you could stick with the 24, but you'd
end up with a smaller wide angle than a d200/12-24 set up!
a better idea IMO is get a d300. the control layouts and form factor will be familiar to a d200 owner, except it's a
better camera in almost every respect. alternately, you could pick up a lightly used d200 for seamless switch-offs
and more intuitiveness (the d300 definitely has a learning curve, but it's worth it for the LCD, the high ISO, and the
better AF over the d200).
you're gonna get a lot of other opinions, but even though i threw out some ideas, try to consider only taking what is
absolutely essential (what exactly that ends up being, is entirely up to you!) sometimes too many choices arent
always a good thing, and it sounds like you have a lot of good gear already -- do you really need to add more?
remember, a purist approach to photography can lend itself to a Rowell-esque naturalist aesthetic--and possibly
better photos. chances are, no matter what gear you have, you'll be inspired enough to not miss what you left behind.