Just the basics, and mostly for a solo campaign. At the end of each battle I would roll a die for each unit destroyed: the appropriate color banner and the unit is eliminated, but a Flag and the unit comes back but starts the next game with one less figure (representing a loss of morale). Any units that survived and were wounded, but were on the losing side would roll a die: on a Flag they would start the next game with one less figure. All units that survive on the winning side come back at full figure counts.
When units come back with one less figure (in the rules above), it is from their normal full complement, i.e. a Human blue infantry unit survives, but is on the losing side with one figure remaining; it rolls a Flag and next game they start with 4-1=3 figures.
I would use the Specialist cards to determine reinforcements, if the unit loss on a side gets too bad, but otherwise I would prefer that objectives on the map actually contain troops. Examples would be taking town X gets you 1 Human Green Infantry, while another might be 1 Human Green Archers, etc. It would also be a nice way to work in Heroes and Treasures.
Still working out my ideas.