All changes I would make:
Singapore Zoo: My pipe dream would be to get some different lemurs on the island near the Gibbons, maybe Brown Lemur or Black Lemur/Blue-eyed Black Lemur?
More feasibly, connect the bearded pig and babirusa habitat and make it a Bearded Pig only exhibit, shifting the Babirusa into the new park. As it stands, both exhibits are terribly small. Also do something about the excessive concrete in the Pygmy hippo exhibits and spruce up Austrailia?
River Wonders: Get rid of the Jaguars. Their exhibit would be better suited to Margay or Ocelot, and as a pipe dream, maybe Oncilla? This would also necessitate the slowing of the boat ride and the removal of those ridiculous rapids. Also combine the exhibits and have a mix with the Peccaries and some primates(maybe the Capuchins?) The peccary exhibit is also too small.
Maybe the return of some Phasianidae to the Panda dome(Hopefully Teminck's Tragopan or Himalayan Monal), or something more exotic than that? Also replace the common fish in the River Gems section with some choice specimens such as Vietnamese Mossy Frog, Water Striders and some other species.
Night Safari: Bring in something not named Binturong, Small-toothed Palm Civet and Asian Small Clawed Otter. Maybe return the Cloud Rats and put the one Spectral Tarsier back on exhibit? It would be interesting to look into other otters as well, but I don't expect that. If possible, Banteng would be nice, as well as a Serow and the Tahr.
Bird Paradise: Mostly perfect, except that there is a glut of Vietnam Pheasant(not a bad thing, though), and photography is an absolute irritant when in Winged Sanctuary. Maybe fixing the mesh and removing the Hooded vulture, while replacing them with the Pygmy Falcon or the Lesser Bird of Paradise. As it stands, the Hooded vulture aviary is too small for them.
I haven't been to Rainforest Wild Asia so I would not comment.