Hi Brett Meyer, thanks for picking this up

Thinking all three in a hierarchy of fallbacks might be ideal (in order)
1.) persistence.xml
2.) PersistenceProvider properties Map
3.) OSGi service registry
4.) OsgiJtaPlatform (default)

I think that all of those options are sensible, but I would re-order 1) and 2). My expectation is that as it's the last possible opportunity I can always use the properties Map to override anything, even the persistence.xml.