It would be nice to give us the option to choose empty for a unit slot on a hero. For example if the hero have 3-4 unit slots once you equipped a unit in a slot you cannot make it empty anymore.
This will be helpful for cases when you can auto combat. Auto combat proved that if a hero has more than 2 units equipped is dumb enough to loose. If only 1 or 2 units are used he wins easily.