I am somewhat of the opinion that the early game and late game should be swapping placed to a degree (difficulty-wise anyhow.)
Early game, resources are plentiful as the Cataclysm has not fully manifested, the only symptom being the freshly undead populace… however as the game progresses the environment should become more and more erratic. Seasons being mere suggestions/guidelines as local dimensional weaknesses and xenoforming take over.
Terrible alien storms ravage much of the structures into ruins, unprotected vehicles and items are reduced to scrap and tatters by exposure within weeks or even days. Strange fauna and flora begin to nest in and overgrow what is left standing.
The early glut of easy pickings you collected remain, but the game becomes an exercise in managing those supplies as the world is overrun and those supplies are threatened by anything from scavengers trying to eat your food supply to the brutality of the elements. Travel to forage for more ‘good’ supplies should become so difficult that there becomes a real REASON to craft and upkeep what remains of your own.
TLDR: Degrade and reduce resources over time: increase environmental and monster hazards simultaneously.
A scene from my imagined ending of a truly ‘Late Game’ character:
Pulling your wretched, mutation ravaged body out of the sewers, burnt-out bionics sparking from the effort as you weld the manhole shut against the chattering clanks and wailing below. A few expended shell casings roll from the tattered rags you wear as you collapse to the ground in exhaustion.
You feel the earth shudder… a distant, rhythmic booming and the alien wooping of ‘somethings’ in the distant. You peer past the vegetation covered mounds of rubble and brace yourself with a trusty rebar spear. Suddenly in a flush of color and madness a wave of mutant creatures dash toward you. One managing to impale itself on your spear, it’s violet ichor stinging your hands as you slide it it off. It had human eyes.
The other ‘things’ don’t even give you a second glance and dash past, howling and yelping as he booming grows nearer. Something, a terribly tall, black chitinous tree swings out of the mist and then another and another; no… not trees… legs.
