Necessary:
fix the annoying flickering vegetation issue when a burrow cam is actively projecting on a screen in the zoo. As it stands, the feature is unusable.
Make elevated feeder usable as an actual elevated feeder instead of having to put it on the ground (related, make it so staff can climb ladders and access enrichment feeders that are on elevated climbing equipment).
Hippo space requirement more similar to real-life zoos. As it is, they are hard to use because of the humongous space requirements.
Not necessary but good:
Fix western chimp social systems so they aren't identical to gorillas.
The former can have multiple adult males within a family group.
Fix the problem with shelters (and habitats) having to be unrealistically large, even for small mammals. I know animal hit boxes are an issue and maybe there's a trade off between this and another persistent issue--animals clipping through barriers and alerts that animals within irregularly shaped barriers are escaped when they aren't.
Smaller rocks and plants available for use in smaller habitats (without looking silly eating up all the traversable space).
Love the idea of cheetah lure coursing/chase enrichment. I remember seeing a feature of how they use these at the San Diego Zoo Safari Park.
Better staff interaction with/anticipation of weather. It's frustrating that they fill the outside feeders (for warm weather animals) right as a bout of cold weather is starting, forcing a welfare issue when animals have to go outside in the cold to eat (in spite of empty indoor feeders), or vice versa for cool weather animals during heat waves.
Water that can be edited to be "contained" by fountains etc. that are above ground
Viewable burrows that can be seen through glass sides of enclosures instead of just on burrow cams.