I like the kind of encapsulation that you have showed but I think it does not correspond to the EJB standard. Maybe it can be used in custom classes.
You really brake a lot of frameworks if you try to make the thing you showed in your code. I don't think Seam can help you if you do not cooperate with him, I mean if you do not stick to standards.
I would be surprised if Seam provides a solution for this tweak.