You might want to create a Lugal-like “Champion” who increases a units combat rolls. Fiddle with the fear test modifiers with great care. If you add factors directly to the Test itself you may create units that can never lose a Fear Test or never win one. The biggest modifier in the Fear Test is +2 for rolling most dice in combat. You want to ensure that the combat modifiers you give get that +2 to the right side. That table may not look much, but I did a lot of work on the numbers in the bands and the modifiers to ensure there are no certainties either way.
Let us know how it goes.