I always thought that a big zombie of sorts that gave out an alert on the map when spawned with extreme speed and strength would be interesting concept to go into, and something that would potentially band together players, like a world event in an RPG such as Black desert. However at the same time we do need to understand this server has always been a PvP heavy environment and that's what our players play the game for.
Increasing the quantity of zombies however is something i'm not particularly for. I say this because as an admin and having the ability to noclip around the map for whatever the reason may be, I get a Birdseye and firsthand view of all of the zombies that are on the map and I don't feel like the quantity we have currently is something that needs to be changed.
Perhaps shifting the amount of zombies into a more concentrated environment where players are more likely to be, rather than have them roaming around the outskirts of the map would be something that might help add a more PvE experience. However right now I think the PvE experience, especially for new players, is in a really good spot right now.