How to implement ASP.NET Identity 2.0 in a layered solution

Question

I am looking for a few recommendations on how to implement an ASP.NET 2 identifier in a layered environment. I have a physically separated presentation and business layer, but all the code examples I've seen for Identity include using EF directly from the presentation layer in the database. Instead of clicking on DB direct, I will have a set of WCF services as my business layer (pretty typical, I'm sure). I make good use of EF below as an ORM, but only from web services, not from the presentation layer.

I assume that the most direct approach will be to create custom implementations of the IUser * Store interfaces, then these implementations will call the internal web services.

Is this a recommended approach or is there another way to do this? It seems appropriate, since this is apparently the recommended way to implement your own user repository, but it seems very difficult to implement all these interfaces (I know that most of them are optional, but I need most of them).