If kills and razings, as well as minerals and gas are taken, that would leave deaths and custom.
Deaths would be a hard one to use in some situations, and there is only the one custom.
Too bad they don't have multiple custom scores.
Here's an off the wall idea, but it would like kinda cheap.
Use the "Leader board control at location".
Make a location that is blocked of from normal game play.
Have a trigger set so as you get a specific experience it creates a civilian or whatever in that area.
Or decrease the number of units depending on your needs.
Set the leader actions for that area, and unit.
It would look a little cheap, but you could theoretically use every unit and have a board that would correspond appropprately to display most anything.