It should be possible to supply EntityManager with a custom ProxyFactory

It is plausible that one might want to handle the loading of proxy classes in their own way, perhaps not using the filename/class scheme doctrine currently comes with.

Currently the only way to provide your own implementation of ProxyFactory is to subclass EntityManager. Even this is not clean since one also must copy/paste the EntityManager::create factory method to get identical behavior.

It would be nice if there was a ProxyFactory interface and one could provide an instance of it to Doctrine\ORM\Configuration when creating an EntityManager.