Add more natively handled resources that the player could enable use of in the “gameplay constants” or one of those advanced menus, up to 6 custom resources could be added (perhaps an overkill ammount, but who knows what someone might want to do with the editor), and allow prices of these resources to be added to buildings and units, and to add harvestable ammounts to doodads and mines, and since they’d have to be treated as resources, things like refunding or other more complicated things would not have to be scripted by hand by the map maker.
However the visual component of the resource (the amount you have being shown in the hub ) should probably be left to the map maker’s discretion, since that allow for more freedom on how to mold the hud according to these new resources.
Also add in that starcraft 2 system for unit control which allows players to select more than 12 units, that adds little tabs the more (in this case) multiple of 12 units you have, of course only for custom maps enableable via one of the advanced menus of the world editor.