I think that Gorilla Rainforest should be reconfigured, retaining Lemur and Gorilla exhibit, but replacing the Treetop Monkey enclosures with a second Gorilla exhibit, and overhauling the Pygmy hippo and "Mandrill" exhibits with 3 display and an off display enclosure for Pygmy hippos, with each on display enclosure being cohabitted with an African monkey species. A new Gorilla BoH could be built between the two Gorilla exhibits, and the area where the existing BoH is could be redeveloped as walk through aviary, or a Colobus Monkey or Mandrill exhibit that could house a small troop of either. This would give the area a nice finish, rather than just the long path with the opposite side of Gorillas.
I would then like to see a new modern Treetop Monkey style precinct either going through Growing Wild, or potentially better matching would be to use a section of TOTE for this, linking in with an expanded Orangutan/Siamang area.