WPF\'s support for DynamicResource is great because this allows users to change the look and fell of a running application.
WinRT does not support DynamicResource th
If you use the MVVM pattern it should be fairly easy to recreate the views based on a switched theme without recreating the underlying data - depending on the way you marry your views and view-models.
Just have multiple theme resource dictionaries and switch which of them you merge with your application resource dictionary, then recreate the view.