Ability to make Barrier shapes, instead of placing a barrier one at a time
personaly I would n ot care much for such an option, since I want my habitats all look different and so somehow give a park a natural look if you include hills, rocks and other landscaping. but I know some people like to build more symmetric. 
For me, it would be nice to have it as an option that could then be modified. I just find placing each individual line of fencing/wall to be a bit of a bore... I'd like to be able to start with something rectangular and adjust/adapt certain aspects of it (for example, an exhibit that is largely square or rectangular with the viewing areas being indented into the exhibit slightly).
I could also see circles being pretty fun for certain exhibit types (e.g., if we wind up getting more small mammals, creating a circular enclosure and then lowering the ground would create a "pit" type set-up that would allow the animal to feel a bit more secure and give the guests easy viewing. I know this is already feasible, but having pre-made "shapes" for fencing would make it easier.
I could also see circles being pretty fun for certain exhibit types (e.g., if we wind up getting more small mammals, creating a circular enclosure and then lowering the ground would create a "pit" type set-up that would allow the animal to feel a bit more secure and give the guests easy viewing. I know this is already feasible, but having pre-made "shapes" for fencing would make it easier.