If at all possible, feel free to take out a civilian skin or two as well. The Reapers will be the best choice for the human faction, as they have big armored trucks. You can also use the Japanese Zombie skins (there are about 3/5 of them, so together with 2/3 civilians and one Karl Blaine skin, we’ll get a good variety of zombies – maybe some with a broken/missing limb?).
Writing the AI code will prove to be the hardest part, but I’m sure you’ll manage. Try getting the admins to open up a forum so we can work out this mod in an orderly fashion. I don’t mind helping with the script, though I never programmed anything in 3d but I’m sure I’ll manage with prioritizing the AI’s reactions towards zombies/military/player.