I use the trangia mess tin as emergency cookpot. Big enough to be usefull, has a little lid and acts like a proper container to store things. In my opinion, for emergency only use. A pot as the main contain is beter, then a cup nestle in canteen options. You can shrink the size of a canteen (take a flexible one), but can't really shrink the size of a pot. Ofcorse unless you have a filled water container.

I do have to say that I generally do not carry a from of cooking pot as emergency gear. Too big and I really do not get that far out of civilisation while being in the outdoors in europe.