Someone else might have mentioned it, but I will just in case not:
I think what you want is too hard to make. It would take some incredible computing power to make every facet of an environment both usable and destructable. Think about how a game like Battlefield 3 can tax a computer (which really isn't that crazy, but just as a base case), then multiply that by about a billion. You're talking an incredible amount of detail to break a fence, then rip off a piece of it and use it as a weapon. Not so much that alone, but that you want that for everything.
For example, your ideal game would mean I could rip the keyboard from my computer and attack a zombie with it, break it over his head, then grab the tower and hit another, then grab a trash can, an Xbox, a small pot, a steak knife, a satellite receiver, and a fan. That covers JUST the noteworthy items in my room. You then have to add that for the 20+ knives in the house, and you have to make things like entertainment centers destructable and usable.
Maybe in 5 years, this is possible, but I just don't think anything short of an asinine supercomputer can handle all of the processing and graphical detail. You'd need a $10,000 computer to play this game, ESPECIALLY if you want to make it open-world--TRULY open-world.
* You would survive on whatever canned/vacuumpacked food you can scavenge from homes and/or markets since all the other food would be decayed
* When you die or get turned/bitten you become a zombie and over time increase in movement speed speed and strength.
* The individual servers should soft-reset after 30ish days, by steadily increasing the zombies' progression to a point where no1 survives the 32-33 day marker.
* The last 10 (maybe 5?) survivors goes on the servers hall of fame.
* People who start after a new cycle has started become zombies instantly