Very envious of your 6 week shoot. Never done India, but shot China many times. Remember that just because you have glass with you doesn't mean you must carry it everywhere. Presumably you will be in hotel or some more or less secure place? I'd bring **minimum** 24-70 II, 50 1.4 or 1.2, and my workhorse 70-200 2.8 (I never ever leave home without that.) I'd consider the 16-35 II. I lilke my 135 f2; light and sharp. Bring 2 LaCie USB-powered external drives, a spare charger for your batteries (bring 3 batteries not 2); and ... make arrangements with someone you really really trust to dropship you another body if yours craps out. I never go overseas without at least 2 bodies and a P&S backup. Bring Imodium too.
Is he opening a camera store there?
Sorry...I travel a lot and I think you shouldn't have to carry extra baggage just for gear unless this the the sole purpose of your trip or if Nat. Geo. is sponsoring you. Your camera should not have a separate life and security outside your own life
and locals get very self conscious if your equipment is bigger than their two wheelers.
All kidding aside, switching lenses in real world situation is a pain particularly if you are traveling - as is carrying a large camera bag. So choosing a couple of important lenses is key. Again, this is assuming your sole purpose is not a photographic trip.
I took two lenses on a full frame during my trip to the subcontinent: 24-105L and 35L.
I also had a coolpix tucked in somewhere (no I did not go over to the dark side...it was a gift).
Most of the Candids I loved were in retrospect taken with the simple 35L.