Really that and some extra end game enemies/zombies. Maybe some bosses here and there, like grace!
Weapon and progression is pretty good. (And if armor I'm sure once it comes out)
Hell add a few more new settings like headshots only, lower the amount of gear you can fine. Raise it, etc
My end game is basically building whatever I want or turn the game harder like no horde bases, Cod zombies style bases, or using crappy weapons like pipe pistols!