This is just in my opinion, if you have nothing nice to say about it please do not post it here...
Also, It doesn't have to happen in the near future, just here to give some ideas.
So, with that being said!
Please read the entire thing, including the bottom.
My list is:
Bikes
Smaller vehicles
Zombie hoards near large towns (Looks like this will happen in the new zombie a.i!)
Improvised Tents
Improvised spear (for fishing.)
Improvised clothing
Making towns look a bit more run down (I personally would just do that when the games beta.)
Making random rare loot locations like heli sits, i.e worn down survivor camps, Military survivor base.

This is ideas for the infection meter.
Stage 1: Character starts coffing, skin turns more pale.
Stage 2: Character starts to begin getting thirsty more often.
Stage 3: (Very shortly after Stage 2) Character starts saying things like. "I'm Starving." As a separate meter, have something like infection hunger.
Stage 4: You begins to go in and out of consciousness, and start making weird grunting noises.
Stage 5: Character will finally die, and in about 1-2 minutes he will return as a zombie, the gear from the characters corpse can be looted, but will no longer be in pristine condition.
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