If there is something that could be greatly improved, then this is the cooperation of troops in the game. Something I would offer to consider:
1. All troops having generals should have the ability to march to the sound of guns in the neighboring region, not just corps and armies.
2. Troops should be capable of entering the region together at one time even if they are coming from different regions. So if a corps in Region A needs 12 days to reach region C while a corps from Region B needs 11 days to do the same, there should be some kind of technique to allow them to do so.
3. There should be a bonus given to troops if the March to the Sound of Guns from a different region than the one where the first engaged unit is. The idea behind this is to account for the outflanking that occurs in reality. Otherwise, there really is no point in separating troops into smaller denominations, and we see huge stacks of troops as it was in the time of the Romans.