Neat mission. We ported this mission over to Take On Helicopters and scattered some choppers around. Using a hind to orbit a city clearing zombies as ground forces advanced was a pretty sweet addition! Feedback:
1) It'd be nice if respawning was allowed, even if it was simple and just dumped you at Balota or something. We were hosting locally so the host couldn't switch to a different slot without restarting the mission.
2) The zombies should do much more damage to full health players. They are already at a disadvantage since they can only do simple melee, having them also not do much damage makes them not that threatening.