[Flow] Achieve loose coupling between packages (models)

[Teo C.]

Hello, 

I'm creating a modular app with some packages that should work together, but still be able to be included in other apps (mainly for going open source, one day).

I'm struggling how to to do this: as an example in a package I have a "Booking" class, which is related (ManyToMany) to a "Person" class in the Users Package, and I do not want to hardcode that dependency in the Booking class via the usual annotation.

I came across this interesting article: 
http://symfony.com/doc/current/cookbook/doctrine/resolve_target_entity.html

It's about Symfony but it's related to Doctrine. Can this be achieved in Flow too ? I found this in the manual:
http://docs.typo3.org/flow/TYPO3FlowDocumentation/TheDefinitiveGuide/PartIII/Persistence.html#on-the-doctrine-event-system

but at a closer look I do not think it's the same thing, or at least I have no idea how to configure it to fulfill my need. Has someone any tips ? Thank you !