I personally love the theme and scenery incorporated into Manta, Cheetah Hunt and Cobra's Curse. The water features on Manta and Cheetah are one of my favorite parts of the rides, and even though it's scenery, I consider it to definitely be part of the theme. I would love something with a Taron type theme and I think Hyena's would be a great choice too. Right now, the Hyena's share the exhibit with the lions, taking turns in different habitats. They could always give them their own exhibit with the ride.
I also think a good idea for a giga would be a Silverback. I read a while back, can't remember where, that this was a rumor for BGT. I think the que would be cool to have a gorilla's in the mist type feel. When you walk through the gorilla/chimp exhibit, there are already misters, so that would be any easy, but scenic que. Plus a great way to keep cool in the que. They could finally redo the front of the park. Get rid of Zagora Cafe and build a new restaurant nearby. They could move the gator exhibit too so the entrance could be near the Myombe Reserve entrance. It would be a lot though, but that's just my thoughts on what I'd like to see.