They have said that creating an Arctic region is practically impossible in the way they would like to have it. Getting ringed seals could be almost impossible. There are not a lot of them in European zoos. For an arctic area could Northern fur seals or Steller sea lions be nice for a pinniped species. For the alternative wadden part, the harbour seal and the grey seal live in the wadden sea. In that part you could also have an aviary for typical wadden sea birds. Such as black-tailed godwits, northern lapwings, pied avocets, eiders etc.
I'm really keen on the Arctic hall, and I'm going to figure out how to forego these problems. There won't be pinnipeds in the Arctic hall though. For the wadden I'm going to indeed make a seabird aviary, maybe even a few. Eurasian spoonbills and Eurasian oystercatchers are definitely on the list, along with other wadden-birds. The seal feedings will probably attract seagulls so those won't have to be added. The only thing I'm worried about is that apart from spoonbills and seals, there aren't many animals in the wadden that can be easily incorperated. For now I'm still rolling with the Arctic, and I'll keep the wadden as a plan B