I feel like with all those dead koalas, they should have gotten enough necropsy reports to learn the problem and never repeat it again. If koalas are vulnerable there I wouldn’t want to risk putting rare marsupials like pademelon or dendrolagus to the same enclosure. I’d use the building to exhibit an animal of low concern such as the brushtail possum (I definitely do not have a secret agenda to push brushtail possums everwhere) or smaller animals like rakali, kowari, hopping mice, and reptiles (which transferring the reptiles could help the Mersus Emergo make some space)
Based on what I have understood from posts by Pairi Daiza (when I was still on social media), media reports and the "Expedition Pairi Daiza" television show, Pairi Daiza actually takes veterinary care of its animals quite serious and puts a lot of effort into those things, so they probably have done necropsies and other research on the deceased koalas. However they don't always report publicly on such matters.
I was however able to find that in three of the koala deaths the Koala Retrovirus was confirmed or seriously suspected, and one animal died of gastro-intestinal issues. From what I understand this virus is strongly associated with various health issues and early death in koalas, and is also species-specific. While it can be transmitted between koalas, as far as I could find it does not infect or affect other marsupials, and would therefore not be a threat to tree kangaroos or pademelons. If any other transmissible diseases were to be present perhaps they could also take measures to decontaminate the building.
Another aspect that has been
suggested by people in discussions at the Laafsekikkers Dutch zoo forum is the lack of a full barrier in the house between the animals and the visitors, which could lead to stress and associated health issues in sensitive species. That could be factor and would also be a factor for tree kangaroos and pademelons, but that is an issue that can likely be fixed by modifying the building and possibly the associated outdoor space.
Personally I don't think reptiles or smaller marsupials would be bad idea for the (former?) koala house, but I would also personally not be opposed to it becoming a wetland and/or forest Australian aviary, as the current desert-themed Australian aviary is quite ill-suited for some of its inhabitants. But we will just have to wait and see what they do with it. Knowing Pairi Daiza, they probably will come up with something that won't go unnoticed.
PS: the last couple of years also haven't been the greatest for koalas in Antwerp and Planckendael, the best days of koala keeping and breeding also seem to be over there for the time being.
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