One particular usecase where this feature could be handy -

We anticipate thousands of small schemas in a specific deployment of our platform which means thousands if not hundreds of thousands of session factories. We have a clustered environment of mysql + jetty and would like to avoid building the sessionfactory more than once.

So for us it would be handy -

1. Build SessionFactory of a schema on first demand
2. Serialize and place a copy of inactive ones on a distributed cache or local.
3. Load it back when needed.
4. Keep the most active schema session factories in in-memory cache.
5. Connection pool and other resources will obviously remain local.