Nicolas Ottaviani, excellent point. It's one that is already fairly well known. In our docs, we state:

The environment should be considered STATIC. Hibernate currently does not support the ability to dynamically add and remove client bundles during runtime. Doing so is typically catastrophic. We hope to better support at least partially-dynamic environments in Hibernate 5.

It's something that I'll definitely work towards, but this may not be limited to hibernate-osgi's OsgiClassLoader. Although I haven't really played with it yet, I'm assuming that hibernate-core itself may need some significant work to handle this as well. But, we'll see. Thanks