It depends on how many people he will be cooking for. With freezer bag type cooking for one person one seldom needs to heat more than two cups of water. That is about a half liter and, in my experience, most of us use a pot somewhere between 0.7 and 1.0 liters for heating water. I use a 0.85 liter MSR Titan Kettle for my cooking now; I used to use a 1.5 liter aluminum pot that I bought used for 50¢ about 15 years ago. It served me well.

As for stoves, the canister stoves are a lot less bother and, IMO, safer than are the white gas stoves. They don't work as well in cold weather and the fuel is more expensive but the fuss-factor is much reduced.

Check here on the Titan Kettle http://cascadedesigns.com/msr/cookware/fast-and-light-cookware/titan-kettle/product and here http://www.snowpeak.com/stoves/backpacking/gigapower-manual-stove-gs-100.html for the Snow Peak Giga, the one I use.

For shorter trips, ie. 1-7 days, canister stoves are lighter than are white gas stoves even when you factor in the weight of the canister. And, smaller pots are lighter than are the larger ones of course.