I would like search options. Mic only specifically. I wouldn't mind them to make the maps a little less rigid when it comes to getting stuck also.
What I mean is when skill is not the deciding factor on how you get stuck, but on who knows the maps better - its is slightly frustrating.
Different types of zombies would be fun. Like a round of 1-8 Juggernaut like zombies, that take a HUGE amount of damage to kill. They need to be semi fast too. And maybe with some sort of Agro, but it needs to be well done so they have a decent chance of downing someone, not like George or the Dogs.