I would love to see NPCs either zombies or others that actually attacked bases. The current zombies are not challenging and need to be increased in numbers. In terms of it being a zombies server I would like to see an increase in zombies. More zombie types. Them actually attacking bases unprovoked to force people to design bases with the zombies in mind. Actually building defences like auto turrets and barricades. I know no one wants to see honeycomb on a scourge server but designing bases with zombie attacks in mind should 100% be a factor on the server.
The entire open world should present a challenge not just the monuments just like in PVP rust. In PVP ofc the open world is made difficult by players and the zombies should give that same feel in the open world. If you isolate the challenge to monuments only I very sadly would have to change server.