Adding dynamically new elements to a JAXWS service JAXB context

Question

I'm using CXF to expose a huge model which contains more than 3000 classes.
In most scenarios the customer will use only 100 classes out of the 3000 but I don't know in advance which ones will be used.
Loading all 3000 on start-up requires lots of memory and takes a long time which makes the development process difficult.
I'm looking for a way to add a minimal set of classes to the context and then add upon demand the missing classes.
The tough part is how to do it in a generic way which won't require each service to handle it explicitly. Another challenge is replacing the JAXB context of a running CXF service.
Any ideas on how to implement such a solution will be appreciated.