Splitting Up EDM To Reuse Functionality Across Multiple Projects?

I currently have an ASP .NET MVC / EF4 project that contains many pieces of autonomous functionality such as a blogging, events, contests, wiki, etc.

The entities used by each system are all mapped to my database through one giant EDM file.

This works well for the main site, but I also have a few personal sites where I want to reuse just the blogging functionality from the mains ite.

My biggest problem is that due to the mac daddy EDM file, my blog sites have to constantly have their database schemas updated to reflect changes made to areas of functionality that they don't use (i.e. changes to the events system).

The only other gotcha is that there are some entities (Users and Tags) that have relationships with entities from each area of functionality, making it hard to simply split each area of functionality off into its own EDM.

With all of this said, I'm trying to figure out the most efficient way to set this up.

Should I go down the road of splitting up the EDMs by each area (blogs, events, contests, wiki) and figuring out a way to maintain relationships for the User and Tag entities?

Or should I just perhaps be creating an EDM for each website that only maps the entities that it will actually need? The only problem with this is that my repository layer takes in a UnitOfWork/ObjectContext, and by creating new ObjectContexts for each site I'd have problems reusing my repository code.