Are you sure you need those other classes generated? It sounds wrong to me. Since you're going to auto-generate them, it seems that the X::Cog, etc., classes would all have the same interface to the X:: class as Thingy::Cog does to Thingy. So it seems to me that you can subclass Thingy without having to change the behaviour of X::Cog, et. al.

Can you give a bit more detail so I can see what you're after?

--roboticus