Class Map Generator for Fluent NHibernate

I think the API has changed since this question was asked, but this works for me:

public class SomeSubclassMap : SubclassMap<SomeSubclass> {
    public SomeSubclassMap()
    {
        KeyColumn("SomeKeyColumnID");
        Map(x => x.SomeSubClassProperty);
        ...
    }
}

I believe KeyColumn is only required if it's different than 'Baseclassname_id'

Note: There should also be a ClassMap<SomeBaseClass> for the base class that SomeSubClass extends.

I've implemented exactly this using (my own) Attribute on the Fluent mapping file to dictate which DB the entity belongs in. I've also got a concept of a 'default' database, and mapping files without an attribute are assumed to reside in the default DB (it may cut down on the number of classes you need to decorate). I then have initialisation code which creates a Session Factory per database, and for each, uses reflection to find all ClassMap classes,examines the attribute to determine which DB it belongs to, and registers each ClassMap accordingly.

A mapping file example:

  [FluentNHibernateDatabase("MySecurityDatabase")]
  public class SystemUserMap : ClassMap<SystemUser>
  {
    public SystemUserMap()
    {
      Id(x => x.SystemUserId);
      Map(x => x.LoginId);
      Map(x => x.LoginPassword);
      Map(x => x.UserFirstName);
      Map(x => x.UserSurname);
      References(x => x.UserOrganisation, "OrganisationId");
    }
  }

Obviously I've defined a list of the DBs that are referenced/used.
My implementation works so far as I've taken it, but I've hit a snag (that I hope someone can help out with):

I've asked my question here: How to identify a particular entity's Session Factory with Fluent NHibernate and Multiple Databases