...For all we know, Primmin remained the station's Starfleet top security man even when not seen, and/or got a steady stream of successors who all failed to make a major appearance in the stories. I mean, how often did we see Kirk's security chief? For all we know, it was Giotto all the time, despite this man only making a single appearance.
Whether there was any gap between Primmin and Eddington that was not filled by another, unnamed top security man... Well, Eddington's dramatic addition to the cast for the of "The Search" sort of suggests that he filled a vacuum. But it could equally well be argued that this Lieutenant Commander was simply the first Starfleet security boss with a rank and billet high enough to challenge Odo's overall authority.
The more interesting aspect there IMHO is whether Starfleet sent any challengers after Eddington turned out to be a bad apple. But after Eddington's story potential had been used up, the writers didn't milk the character's departure for further dramatic value by explicitly establishing that Starfleet now trusted Odo and was ashamed of earlier distrust - or perhaps had ceased trusting Sisko, too, and had given up on trying to control the wormhole through the station, preferring a more direct control via Starbase 375 and its starship forces. After all, Eddington's departure coincided with the abandoning of Bajor's neutrality in the middle of major external threats, and the arrival of warfleets.
One thing I wish they would have done though would have been to have a Bajoran counterpart to Bashir.
And a Bajoran engineer to match O'Brien (although they did do some stories with Bajoran apprentices to O'Brien). And a Bajoran scientist to match Dax (although there were visiting scientists and some stuff on Bajor not really appreciating scientific study of the Celestial Temple).
Timo Saloniemi