I think a time based Survival would be good. It would work like this:
>No Waves, the longer survived = more zombies spawing
>Players that die would wait for X zombies to be killed, then respawn (around 50 Zombies)
>New power up respawns all players straight away
>Respawned players are invincible for 15seconds, to give them a chance
>Special Zombies like Minions spawn every 5minutes
>New Power Up stops zombies from spawning for 30seconds
This Doesn't need to wait for DLC4, just make it an option in Custom Games.
What do you guys think?