[22Kston]

I have a idea what to replace the removed zombies with.
I was thinking of a travelling NPC caravan, moving along the map following the road.
The idea is to have armed NPCs guarding a few vans/trucks. There could be more vehicles following with different difficulties to take down.
The first or the last trucks would be easier to take and would have NPC with guns guarding it,
the middle truck should be the hardest, guarded by NPC with long range sniper rifles or RPGs/Bazookas, or a mounted maschine gun.
It can even be armored and require the players to use explosives (C4,rpg, wahtever) to disable it and break in.
around the caravan there could be a few footmen with only pistols and low loot.

[RustedCreeper]

Possibly a group of cavemen crowded around a campfire, then if disturbed they'll attack you.

[G3wd B3rg3r]

Since there's going to be a reveal, it means t hey are working on that already, we just don't know what it is. So, time for ideas is over, although I like yours. I feel like a armed threat would up the anty a bit more while also giving people that 'humanoid kill' itch, but with a lot more risk because they can shoot back instead of just running at you. I also feel this would solve the 'where do these guns come from?!' problem people seem to have trouble getting over like the game takes place in the 12th century or something.