Allow search of active relationships during a custom range of dates

We make heavy use of relationships on our CiviCRM implementations to record a variety of situations: volunteer relations between an organitzation and a volunteer, grants concessions relations between an organitzation and a user beneficiary, etc.

Start and End Dates allows us to limit the time period in which the relationship is valid. Unfortunately there is no way to do a search of all the relationships that were active during a given period. See detailed discusion here.

A first approach would be able to search for empty dates as can be done in Relationship Reports. See how here.

A second and more accurate solution would incorporate a search field that allows you to filter the date range for which the relationship was active.