I have seent hat done before and it is a good idea! I like the ideas of having nested mugs like that because they dont take up too much space. I want to go with a Nalgene style mug system though, becuase I like the wide mouth better than the narrow mouth of the issue canteen. I actually dont even use them at all most of the time. I use my nalgene bottle more often than not, but I usually carry my camelbak for water. I use the water bottle to have a rapid source (for lack of a better term) of water for cooking and hygene. They work out better in colder environment as well.

I am getting very excited about getting a mug now. I cant wait to get out and get one.