Would you like to see some bushcraft/survival elements? Ie being able to make fire, build shelter (done ), find and purify water, have to eat/drink/sleep and protect against the elements? An apocalyptic game is made for this type of stuff imo. Imagine the scenario, you're dying of thirst, you find water but its contaminated, you need a fire but have no firewood, you collect some wood, build a fire using your last bit of kindling, manage to boil some precious water just enough to get you to the next town. That is what a post-apocalyptic survival game should be imo, not simply gluing a battery to a piece of wood and getting a laser canon added to your inventory.
*edit also add severe crippling diseases/infections. Like catching a plague where NO ONE will talk to you. That would make a truly great RPG.