I added to new-file-storage our group-data package:
https://openacs.org/new-file-storage/one-file?file_id=403
And attribute package:
https://openacs.org/new-file-storage/one-file?file_id=404
This has helped us do what you've asked. Group-data is for groups, and Attribute is for individual objects. For instance, if you wanted to keep "cellphone number" data on one group, you'd create a group-data of "cellphone number" on that group, and the use the api to add/remove/view/etc that value.
Any comments or suggestions are appreciated.