So beautiful, small & endangered geckos that can become just as popular as other reptiles with enough education are not accepted, but the New Caledonian sea krait is?
I have seen several gecko exhibitions like the one in Plzen zoo that are quite popular with the public, as well as the anole collection at California Science Center. It is the zoo's responsibility to provide enough information about the uniqueness of those creatures. Laticauda saintgironsi on the other hand is completely absent from captivity, has shown to be very difficult to keep alive, requires an expensive and possibly unrealistic diet and is illegal to import.
Of course, it is your own speculative exhibit. But I recommend a healthy focus on education and conservation when you build a plan for small islands with so many rare endemics. The all-time focus on big or colourful animals is the worst thing a zoo could do.
The wandering whistling duck (Dendrocygna arcuata) also lives in New Caledonia and is a fine species for a walkthrough enclosure. Same goes for the zebra dove (Geopelia striata). This pigeon is not native to New Caledonia so you could inform visitors about invasive species.
The purple vampire crab (Geograpsus grayi) is also found in this range.
Sorry for giving a disagreeing perspective. I am a great zoo fan, I love every single species I have the opportunity to come across. But even I, every time I visit Berlin Zoo (the one with the most species), struggle to see every species of their +1k collection. This is because the zoo is only open for 8 hours in one day, some species in aquariums or terrariums are not found, and I also have to eat and rest during the visit. My solution for that is to return the next day or the next year, but 99.9% of zoo visitors do not do that. Not every zoo visitor is a taxonomy/biodiversity nerd like me, and I recognise that.
Now imagine a family with kids (the most typical zoo visitor) who need to constantly stop to eat, drink, to toilet, play in the playground, etc; with exhausted parents that spent the whole day running following their kids, and kids that have no more than 10min attention span. I really do not think the average visitor has enough capacity or interest to look at every single species, every single educational board, and get every single story. Is it worth having those species and education? Of course, it is, but we must be realistic. By the end of the day, zoos are businesses and their ticket revenue (which is also spent on conservation and education) does not rely on a difference in a room with 10 geckos or 50 geckos. Visitors will attend in equal numbers either way, but the logistics of keeping 50 terrariums are much higher than keeping 10 (energy, food, labour, staff). Zoos have to be cost-effective. It's not the 0.01% of zoo nerds (me included) that cover the operational costs of a zoo. Is the 99.9% of people that leave the permisses happy if they have seen some nice animals and got some know something new about wildlife. Hence the post being called "realistic".
And the vision that 21st-century conservation should be focused on single-species conservation is pretty much outdated. Nowadays protecting an entire ecosystem is proven to safeguard more biodiversity than species-focused conservation. Using the most popular species as flag or umbrella species is the best strategy to capture the public's attention. People donate to protect the tigers and their habitat, and by protecting tiger habitat every species from the little frog to the big elephant that lives there gets protected. And you do not need to exhibit a frog or an elephant to explain to the visitor that the tiger's habitat has tremendous biodiversity, which includes frogs and elephants.
In recent zoo visits to newly refurbished exhibitions (like the Alfred Brehm House in Berlin Tierpark), I have even seen more educational material dedicated to environmental problems (deforestation, climate change, pet trade, invasive species, pollution, etc) and solutions for people to take home (recycling, conscious purchasing, energy saving, meat/fish-consumption, etc) than material about the species being exhibited. In my opinion, I prefer a zoo visitor that leaves the park with a good picture of the global environmental/biodiversity challenges and exact solutions to tackle them than leaving the park as a gecko nerd.
Unfortunately to say, but zoos are made for the masses, not for the zoo fans/nerds.