By far the easiest way would be to just add it to your custom factions by including
<A_Trading>3</A_Trading>
in the file found at User/My documents/My games/Elemental/Units
If you want to apply it to the core races, make a copy of CoreRaceConfigs.xml and edit in the line for every race. Then put your copy in your elemental install dir under the /Mods/ folder.
