What we want to achieve as a first step is...

Co-op game

A number of players can connect to a dedicated server and play with each other in a single session/world

Goal

The main goal is to kill enemies. From the game design perspective, players are bounty/monster hunters.

Content

Bots

[At least] two types of enemies to shoot: aggressive (will attack on sight) and fearful (will run on sight)

Weapons

AKS-74U, G-67 grenade, M-9 knife

Tactical-based Shooting

Reloading is not arcade-like but rather magazine-based. Weapon damage is lethal: 2-3 shots is usually enough for bots and players.
Think of S.W.A.T. series or Takedown: Red Sabre.