Thanks for this amazing research! It's sobering to see that most of the animals that have been a massive drawcard for the zoo over the decades have been phased out. As you've said here, phaseouts are sometimes necessary, but a zoo's priority should be looking into new species to replace the phased-out ones, not building more play spaces when the zoo already has several playgrounds, and Western Springs is right next door.
Personally, I would prefer to add the ring-tailed lemurs to the phase-out list, as much as I do like them, and replace them with red-ruffed lemurs. And I would prefer also to retain the baboons, or if they are phased out, I'd like to see them replaced by another African primate species such as colobus or vervet monkeys. I also like the idea of okapi, as the nyala and waterbuck are currently the only antelope species and the waterbuck look like they'll be phased out also.
I'm glad to see animals such as the Bornean orangutans and Sumatran tigers enjoying such popularity, although I personally would love to add yet another primate species to the South East Asia Jungle Track, possibly a monkey species (proboscis monkeys would be a HUGE drawcard) or a second type of gibbon in addition to the siamang (I think Australasia is phasing out lar gibbons and other species currently in the breeding programme are Javan and white-cheeked gibbons, but I'm not 100% sure on that). Also, as fond as I am of our siamang pair Intan and Kera, I would consider transferring them to another zoo and importing a breeding siamang pair to make full use of the extensive habitat. Possibly, in the future, I would also consider establishing a second orangutan colony, if I could design my dream South East Asia precinct!