I think most of what you need is pretty straightforward. Certainly, for the battery charger, I'd simply take whatever you use now for a charger and buy a convertible plug that will work there. Most plugs in India are what are called Type D, which consist of three round pins (one of them is a ground). Voltage, interestingly, is 240, twice the standard here in the U.S. So be sure you get a "step-down" converter to change the 240 volts to 120, or get a charger when you get there that's designed for local power output. I wouldn't worry about the surge protectoryou aren't going to hurt the batteries if you get a surge. It'll just be another thing to carry.
There are two ways to secure your items. One is to get a bicycle-type lock that can be threaded through pack straps and the like. Of course, a thief can always just slice the pack straps. They're not really after the pack, anyway. By far the best way to go is with a Pacsafe gear protector. The Pacsafe Backpacker ($60 to fit medium-sized pack; www.pac-safe.com) is a stainless steel mesh that wraps around the pack. Very tough, and even if a crook has wire cutters, he will have to cut through a LOT of wires to free the pack. And the Backpacker is pretty light. It fits into a little carry pouch and weighs just over a pound.
For a bag liner, I'd get one made of silk. Light, comfy, and useable as a stand-alone bag in very warm weather. The Cocoon Silk Mummy Liner ($50; www.rei.com) is ideal.
Have a great trip!