I don’t think what you are trying to do is supported. From the @Managed javadoc:
Abstract classes
A managed type can be implemented as an abstract class. All property getters and setters must be declared abstract (with the exception of calculated read-only properties). The class cannot contain instance variables, constructors, or any methods that are not a getter or setter.
The key part being that all methods must be getters or setters. @Unmanaged is intended to be used with property getters.
OK, I misunderstood your question. I thought you wanted help making that work with the current implementation, not that you were making feature suggestions.