Transitive invites?

[glpatcern]

Currently, invites are ad-personam: When Alice@A invites Bob@B and Bob accepts, they can then exchange shares but nobody else from their organizations.

What if Charlie@B also wants to share with Alice@A? What would be the implication of making invites transitive, such that some subset of users @ B (to be defined) are allowed to share with Alice@A, or even any user @ B is allowed to do that?