Suhail just posted, on the VS Team Architect blog, details of a power tool that the team has been working on, the ability to define class libraries on the design surface, please check it out and give feedback: 

Currently planned scenarios:

· View Class Library projects on the AD (Note: projects = Visual Studio Class Library projects)

· View references to Class Library projects as connections on the AD

· Create Class Library projects from the AD

· Create references to Class Library projects from the AD

· Synchronize properties between Class Library projects and their representative applications on the AD

o (Notice the properties in the grid e.g. Class Namespace, Language, Assembly Name etc.)

· Create and use Class Library applications and references on the System Designer (SD)

· Navigate to the class diagram for a Class Library application.

Source: VS Team Architect Blog : Team Architect Power Tools