AFAIU it's not possible to contribute SF aware services through a standard integrator as of today. Instead one needs to register a custom service registry factory for the SF scope which just exposes services retrieved from a static list of initiators.

Couldn't it be an alternative to create all those services contributed by an initiator which implements SessionFactoryServiceInitiator through a default implementation of SessionFactoryServiceRegistry and manage them on the SF level? This would allow to specify all initiators in one place (the integrator) and would avoid the need for a custom SessionFactoryServiceRegistry, its initiator etc. Of course this would require changes on the ORM side.