Yes, bring them on
No, I'm too tired of them elsewhere
Zombies, mechs ... Whatever. A new enemy type would be nice.
The story of the game doesn't include zombies and that's pretty much why there will never be zombies. And I really don't want them in the game anyway. It's 2016 not 2010.
Yes to zombies .
Just open it up to the modding community and let people make it into whatever they like .