allow multiple relationships of the same type on constituent record
Example provided: a board member may resign from the board then, years later, rejoin. User would like option to add "Board Member" multiple times as relationship with the different start/end dates.
We have a similar need to allow the same relationship to be added between two constituents at different points in time. Although some relationships are not on and off again over time (e.g. parent/child), there are certain relationships that may be on and off multiple times over time (such as the board member example given by OP).
It seems that this ability could be added by making the [UIX_RELATIONSHIP_RELATIONSHIPCONSTITUENTID_RECIPROCALCONSTITUENTID_RELATIONSHIPTYPECODEID_RECIPROCALTYPECODEID] index on the RELATIONSHIP table in CRM non-unique or perhaps incorporate the Start/End dates into the index to maintain uniqueness.