I think it could become quite a good, yet small, centre for endangered animals. It may be tricky and a bit costly but I am sure it is possible.
I have visited and whilst there I had alot of ideas on the zoo... First of all, get rid of the petting farm, it takes up alot of space and could be used for something alot more exotic and endangered eg. Walkthrough Aviary, a small hoofstock paddock for example, duiker or Kirks Dik Dik...
Move the Rhea and EXTEND the Leopard Enclosure, it could be a good 3 times larger, I cant stress this enough!
Use the rabbit and guinea pig rooom as a small mammal room, maybe nock a few through and have a larger Porcupine exhbit. Im unsure what you could do with the reptile area but the presentation area could be great for education!
Nock through the Kookaburra aviary and extend the fox paddock maybe...
The possibilities are endless and once all the rescues have moved on/passed away it could really be fantastic, just needs someone to get it up and going.
Its great to know you may be buying the place and id like to know what you will be doing/have plans for?