How: Have the fieldset be an attribute on the Item that you can filter/query just like any other fieldtype/attribute on the Item.
Why: The fieldset is used to categorize items. It would be helpful to look at one category and not have to replicate that in another fieldtype/attribute in order to query it.
For Who: Enrich users who use queries
Impact: High, big time saver
Additional context:
Please, add your suggestion and feedback above to add to the insights used by Product team when deciding priorities and direction of the Inriver PIM.
The fieldset is usually one of the first 3 columns on the export, so you can filter that way (in excel).