just like gta v merrywheather service there should be active or at least passive help from coalition to players who did join coalition by ensign,major,or something like that.NPCs should defend coalition member player like if you ensing there should be 2 coalition npc help you on foot, if your rank is higher like if you are a MAJOR GENERAL in coalition a helicopter backup and also a van with 4 coalition soldier should come help you that will encourage players to do missions and avoid agressive attitude.also that should be very cool imagine u are a villian who attacked coalition member and few minutes later coaliton npcs come help him
This would be realy cool but it may be hard to add to the game. Maybe instead there should be a big coalation base and if you joined them they wont shoot at you but if you joined the other guys they shoot at you also they would shoot at zombies. It shouldnt be to hard to do. The npcs firing can be just turrets that look like humans.
But it should be just a placeholder untill friendly ai works good. But i would live to see what you recomended.