We have the need for another, larger "bucket" of classification into which we can put collections and exhibits. The general description of what we need is online at https://docs.google.com/document/d/1oWvlUqwyZeU50mCbXUSHDq6IXma-8aWni6AD6Vg3pEY/edit?usp=sharing. Please respond to firstname.lastname@example.org with questions and/or a quote for this development. Thanks!!
Quick observation: the general description linked to says that it should be built either as a plugin or as core changes to be submitted to Omeka.
From the Omeka side, I'd say this should definitely be a plugin because of the very project-specific functionality involved. Moreover, there are many additional reasons that a pull request to the core might not be accepted, and so any work on this as changes to core would basically lock you in to the version of Omeka it is built against -- meaning no bugfix or security updates.