I was re-reading a thread about entrenchments being "over powered" and I had a thought, why do entrenchments offer no bonus to attacking troops?
Now before you laugh and say, silly man you have to get out of your entrenchments to attack so how can they help you?, consider the offensive potential for entrenchments. Attacking an entrenched position across open ground is suicide. Digging in allows you to get around the problem, because digging approaches allows you to remain in cover while closing the distance with the enemy. Good approach trenches can get to within 50m or less of a defensive position. Troops, supplies, and artillery can be brought up close and in relative safety in preparation for an assault, and the defenders have a hard time tracking troop movements. When the order is given to go over the top, the first enemy line could often be taken in the initial rush. After that, things get messy for the attackers, because attacks tended to break cohesion as they got further away from the LOD and the enemy counter attacked. But things are equally messy for the defenders in the counter attack, because they have to get up and expose themselves in order to eject the attackers from their front defensive line. When you look at causalities from assaults that started from entrenched positions (or siege positions), generally attackers and defenders have roughly similar numbers of causalities.
What could this mean for the game? A simple solution would be to make the real entrenchment level of a defending element the difference between the defending stack and the attacking stack's entrenchment level. Defender dug in at 6, attacker is dug in at 2, the defender receives an entrenchment bonus of level 4. (This would be similar to how the offensive/defensive stats of leaders stack up against each other when calculating hit chance). In the case of assaulting a structure, any fort bonuses would be unaffected.
Now all of this really only comes into play if you have two stacks sharing a region, which is pretty rare. An attacker from outside the region should be expected to face the full force of entrenchments when trying to force his way in.