Retorts are ok for holding foods safely, but need some sort of water bath or heater, if you are going to have a warm / hot meal. There some issues with re using that water, as the packaging can leach off certain chemicals, thus making that water something other than potable. It may be ok to shave with, but not drink or brush your teeth with.
Most MREs use retort pouches to a large degree. The retort does not break down in nature, and over time, a build up of these materials can be an attractor to critters and vermin.
Some good things, a retort pouch, opened length wise on a seam can make a quick container for all of the other components of an MRE.
They can be rolled and made smaller, if you can carry it out. low impact camping (Leaving nothing but foot prints) or recon missions, as an example.
This also brings to mind the MRE heaters, which are water acivated, generate heat but reacting to the water and give of hydrogen gas, so ventilation and not having it next to your body is important.
As the heaters are reactive, they are considered to be a hazardous waste unless expended. Note if you are familiar with dry ice and water in a confined space, heater packs can do the same.
The Hydrogen gas is flammable, and in close range stinks, but not half as bad as the heat tabs for Tommy cooker stoves.
Just a few comments.