Two cents on asp.Net MVC localization
As an asp.net MVC application is an application and not a site, as introduced by asp.net 2.0, IResourceProvider does not seems to be available.
The data annotations class rely on strongly typed classes to retrieve resources. The attributes uses reflection and not the TypeDescriptor, even though they are located in System.ComponentModel sub namespace.
Therefore, I wonder if it would not be possible to create a new custom tool to generate the strongly typed classes, that would delegate the calls to the IResourceProvider, possibly modifying the outputs from System.Resources.Tools.StronglyTypedResourceBuilder.