Reading the forum and topics related with the factions in one of them said about the zombie faction. I thought best to take the Alien faction NPCs from hl1.
Home building such as a portal into the world hl1 zen. The first combat NPCs Houndeye, builder Bull Chicken, the second Battle NPCs Alien Grunt, and the third battle NPCs Baby Gargantua (Gargantua just seems too big).
At the beginning of the game base is Big Momma guarding the base.
Built: Headcrab turret (turret fired headcrabs Cator getting on rebels or combine turning them into zombies), the force field (as in comibne Toko looks more like), a mine with the Snark (mine is going to come out of it Cator snark).
Resources, I also think that antlion larvae Cator used as food.
Thinking of everything.

I am Russian so Sorry for the mistakes I'm just learning english.