Extension methods on a poco class in subsonic?

Question

I'm considering switching from fluent nhibernate to subsonic as nhib just seems to have a MASSIVE memory footprint which I'm really not enjoying, but I just want to check how subsonic (the simple repository probably) would cope with:

• adding extra fields to a database: at the moment I can map a dictionary value to a field in the database which is VERY cool, is this possible in subsonic? (or anything similar?)

  FWIW: DynamicComponent(x => x.PropertyBag, GetDynamicComponentPart); where propertybag is a Dictionary.

• many to many relationships

• cascading saves/deletes
• mapping a complex object to an xml or varchar(max) column (seralize it to xml obviously)