Good on the STL people for pushing this. There have been people furloughed on the AA side over the past two years for the exact same issue. They were low on the seniority pole, but had the bad luck to be domiciled at a base that "had no overage" therefore overage leaves were not offered in that base.
As much as scheduling loves to deadhead DFW people to Miami to cover Miami trips while deadheading MIA people to DFW to cover DFW trips, or ever screwier assignments, I'm sure they could have figured out a way to cover any shortages that might have resulted from offering OVLs system-wide, not just in the base(s) with the overage.