Why not add another NPC at some stations that could offer a search service for a fee (% of the mission reward credits) to find the missions we want from systems in close proximate of the mission broker.
Search for missions that reward material X.
Search for different type of missions.
Example:
I want to find passenger mission that rewards material X. The Mission Broker list any available missions within X Ly.
Search for missions that reward material X.
Search for different type of missions.
Example:
I want to find passenger mission that rewards material X. The Mission Broker list any available missions within X Ly.