I don't know if it would sate your appetite, but there are icons which you can switch on in the options, which show what other units are there...(see the red circles in my screenshot)
In fact, the icon displayed in an area is the main unit....so if there are militia and artillery in a region, then the artillery icon is displayed...likewise when a leader is in an area, regardless of what other units are there, the ranking leader is displayed. It makes sense being as leaders are absolutely paramount to combat.
Trust me, if you want to know where you are going to make a breakthrough, you will be scanning you leaders...then looking at infantry, artillery, militia and prob in that order.
I know it might seem strange, but because of the importance of leaders, it soon falls into place why they are displayedas the default icon when they are in a region.