We all know how vanguard zombies dropped with the least amount of content of any zombies game ever.  On top of that, the content we were given was not complete and 95% of the community is dissatisfied.  The big issue here is the lack of replayability and a simple way to fix that is to add more maps.

Now, they already have the majority of Shino in Der Anfang, so in theory it shouldn't be that hard to make it it's own standalone map.  They also have the cool windmill area and stalingrad in general which they could make their own maps.  They wouldn't even need to add any main Easter egg or anything.  Just the perks, pack, the altar, and some ammo crates and crafting tables.  

--For Treyarch/Activision (if they ever see this)

I feel like this is 100% doable since the assets are already in the game and not only would be current players actually be satisfied, but it would also increase the sales of the game because I've seen so many people refuse to buy the game or refunded because of how terrible the content is for the game.  I've seen at least 20+ posts on people asking why shino or stalingrad isn't a survival map also, and it baffles me why treyarch is so against making survival maps nowadays.  Just take the maps, make it round based, and make us happy.  Please.  Listen to the community for once.