I like the idea of having the Spider Monkeys in the former baboon enclosure; it would be even better if they could share the enclosure with a species like Mara who could make use of the ground area. Or even an extension of the Tapir complex if they wish to have more space.
The combination of Brazilian tapir, Black-handed spider monkey (and a Cape Barron goose that believed he was a tapir) always worked well at Hamilton Zoo.
The baboon exhibit would allow for a large spider monkey troop to be held, with regular breeding so females can learn maternal behaviour by observation. It’d be a shame to loose them from the zoo altogether, though a redevelopment of Treetops is needed and it’s a good opportunity to redevelop it for an African species to achieve a greater sense of geographic theming for this precinct (with gorillas being the main attraction). The Rail Gate end of the zoo would then have the foundations of a South American zone. It wouldn’t be hard to add a couple of tamarin exhibits to this area.