Most of the information suggested as candidates for inclusion is associated with individual specimens in a collection. In a catalogue of collections such information would, as I understand, need to be aggregated on the level of the containing collection.
For example, if information on the collectors of the specimens is desired, a list of collectors would need to be aggregated from the specimen level and connected to the collection record. In the case of a specialist collection which was brought into being to assemble all specimens collected by a particular collector, that list would have a single entry.
Such aggregated information would need to be provided by the data providers or, in an advanced scenario, might be scraped by the catalogue from information endpoints representing the collection contents.
I think while all of this candidate information - and the corresponding services described in topic 2.6 - is potentially useful one should carefully consider in which cases such aggregated information corresponds to use cases of the catalogue. This might get really complex really quickly, and for some of these enquiries the information facilities offered by the collection resp. its holding institution might be better suited.