That is a terrific idea in my opinion. That would also increase the value and usefulness of several things I was thinking of adding to the game... little modules that add onto your PipBoy that increase functionality. For example, if you get a motion sensor module, you can install it and toggle that in the map screen, without giving the PC (sorry, I use PC and 'you' interchangeably) a hassle and using the active item slot. A geiger module could easily, in real-time alert the player to radioactive food and drink. Storage of water could either be in regular cantines, or if you wanted to get really technical, here's a terrific idea:
Instead of stupid litte Micro-fusion Cells and Small Energy Cells, instead of batteries that run down on the geiger counter and radar unit (or PipBoy, for that matter), just use hydrogen stored in the form of sodium borohydride. Then, as you use the hydrogen to power your equipment, the excess pure water could be added to your cantine. What's nice is that it simplifies things in the long run (powering your car, ammo for energy weapons, water, etc.). You can refill your borohydride at every town, and/or, if you get solar panels on your car, then the car recharges the hydrogen supply. Of course, some of the energy from the panels would have to go to a dehumidifier unit to extract water from the air, so it can be split by electrolysis. Also, the PC can buy containers to put inside the car that contain water so the electrolyzer and player can use/refill with. If the player becomes dehydrated, their hp lowers, stats lower temporarily (just as rads do), and you lack the ability to run.
Enough about water, though. Here's how food should go. You can buy vegetables and meats, etc. from vendors in each city/town/village. You can also scavenge. The neat thing is that you can tell your party members to scavenge. Each party member should have SPECIAL stats and skill percentages just as the PC does. If the PC reads a book/manual and is done with it, you can hand it to your NPC's for them to read and increase their skills. Also, depending on their speech and intelligence, they can convey their abilities to the other characters. Anyway, you can tell everybody in your party to scavenge, and depending on their outdoorsman skill (determines how much and quality of food) they will bring back some food and water. That way you don't have to worry too much about running out of rations/water in the desert. And if you have the geiger counter module, it automatically scans for rads. If you have, say, a lil' chemist kit, or a mini-spectrometer in your PipBoy, you can also detect poisonous chemicals. Finally, another characteristic, disease, should be factored into the player's statistics. Pathogens can be detected with a rather bulky microscope, or later in the game you can add a micro-magnifier module to your PipBoy to scan the substance/area. Depending on your science, doctor and/or first aid skills, intelligence, outdoorsman (to a lesser extent), and perception, you will find (or not find) bacteria and viruses in the target substance. Your equipment and outdoorsman skill also determines how many times in a time period this is checked.
Also, on the 'stillsuit' line of thinking, wearing Power Armor will decrease your use of water by a large factor. It will recycle your water, and distill/filter the urine. Of course, it sounds disgusting, but astronauts do this all the time, and power armor was made at least some fifty years from now. To think of the advances of polymer technology; permeable membranes, possibly even selectively permeable membranes. Of course, this would add a little complexity to the game, but I believe it would serve to add more depth to the game, and more fun in the process.
