Understood, but there is so much more that could be done onsite. Without breaking sweat, I could (and I feel certain that others can!) walk round Whipsnade and identify spaces where Gelada, a gibbon species, at least one more large (and three or four smaller) cat species, Brown or Striped Hyena, African Hunting Dog, Polar and Spectacled Bear, Brazilian Tapir, Black Rhino, and a good half dozen extra herd species (Hartmann's Mountain Zebra, Persian Fallow Deer, Addax, Musk-ox and Mishmi Takin, anybody?) could be held, without turning the site into a concrete jungle.
A good few extra climate tolerant bird species (say Red-breasted Goose, Harlequin, Long-tailed Duck,any number of pheasants, Oriental White Stork, Steller's Sea Eagle and Black-necked Crane) also spring to mind as being animals that any German zoo aficionado would not be unduly surprised to see there.
I agree with many of these suggestions. I always think it a great pity that Whipsnade has turned its back on one of its greatest glories: apart from the penguins, there is now nothing to see with view over the escarpment as its background. I can easily imagine a spectacular gelada exhibit and perhaps one for Japanese macaques too. The old lion and tiger exhibits would need some expenditure to provide modern barriers in place of the old bars, but would do nicely for hardy species such as bobcat, Pallas' cat, raccoon-like dogs or coyotes. Could the old pit used for the Kodiak bears be extended for a hardy goat or sheep species? Musk ox and or takin would be wonderful, but would require very robust and extensive accommodation which would be more expensive.
I'm less sure of the tropical species such as hyaenas and hunting dogs, unless they can be given more sheltered positions, but I would love to see nice herd of deer in one of the big paddocks again - white-tailed deer or mule deer would be nice to see.
I always feel that Whipsnade is not really the place for most birds. The trend is going against pinioned waterfowl and cranes, which were formerly the nucleus of the collection and I'm not sure that modern aviaries with lightweight mesh would withstand Whipsnade's winters. But a robust walk-through with hardy birds could work well in the Bird Wood.
Regrettably I think the sea duck idea would not work: they need expert care and very clean water.
Alan